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Frequently Asked Questions

International Studies

U.S. Participation

The United States participates in multiple studies measuring different subject areas, or "domains," for different target age groups. Below is a figure summarizing the studies, subjects, and target population(s) for each international education study.

International Studies Across the Life Span

The International Studies Across the Lifespan figure displays the comparative international studies that the National Center for Education Statistics (NCES) currently conducts in the United States–from early childhood to adulthood. The figure also identifies the target age groups and subject areas or topics of the studies.

Detailed descriptions of the studies are below:

IELS — International Early Learning Study
IELS is an innovative new study designed to provide countries with a common research-based language and framework to discuss how to improve the early years for all children. IELS consists of a play-based assessment of 5-year-olds’ knowledge and skills in four key areas: emergent literacy, emergent numeracy, self‑regulation, and social emotional skills. Data from IELS provide the opportunity to better understand the skills and competencies of American children at the beginning of primary school and how they compare to the skill profiles of 5-year-olds in other countries. The United States participated in the IELS 2018 Pilot Study. The second cycle of IELS is currently in progress. IELS is coordinated by the Organization for Economic Cooperation and Development (OECD), an intergovernmental organization of industrialized countries, and is administered in the United States by NCES.

PIRLS — Progress in International Reading Literacy Study

PIRLS is an international assessment and research project designed to measure reading achievement at the fourth-grade level, as well as school and teacher practices related to instruction. Fourth-grade students participating in PIRLS complete a reading assessment and questionnaire that addresses their attitudes toward reading and their reading habits. In addition, questionnaires are given to students’ teachers and school principals to gather information about students’ school experiences in developing reading literacy. Since 2001, PIRLS has been administered every 5 years, with the United States participating in all past assessments. PIRLS is sponsored by the International Association for the Evaluation of Educational Achievement (IEA) and conducted in the United States by NCES. The results for the most recent cycle (PIRLS 2021) were released in May 2023.

TIMSS — Trends in International Mathematics and Science Study
TIMSS provides reliable and timely data on the mathematics and science achievement of U.S. students compared to that of students in other countries. TIMSS data have been collected from students at grades 4 and 8 since 1995, generally every 4 years; the United States has participated in every administration of TIMSS. In addition to the mathematics and science assessments, questionnaires are given to students, their teachers, and school principals to gather information about the background contexts for learning. TIMSS is sponsored by the International Association for the Evaluation of Educational Achievement (IEA) and conducted in the United States by NCES. The next cycle of TIMSS is scheduled for 2023.

In 1995, 2008, and 2015, TIMSS Advanced, an extension of TIMSS, was conducted to measure advanced mathematics and physics achievement in the final year of secondary school across countries. The United States participated in TIMSS Advanced in 1995 and 2015.

ICILS — International Computer and Information Literacy Study
ICILS is a computer-based international assessment of 8th-grade students’ capacities “to use information communications technologies (ICT) productively for a range of different purposes, in ways that go beyond a basic use of ICT” (Fraillon et al. 2018). First conducted in 2013, ICILS assessed students’ computer and information literacy (CIL) with an emphasis on the use of computers as information-seeking, management, and communication tools. Thereafter, increasing international recognition of the importance of students’ abilities to recognize and operationalize real-world problems using computational formulations led to the development of the computational thinking (CT) component within ICILS. The second cycle of ICILS was administered in 2018; it continued to assess CIL, but it also assessed CT in the newly added, but optional, assessment component. ICILS is sponsored by the International Association for the Evaluation of Educational Achievement (IEA) and is conducted in the United States by NCES. The United States participated in ICILS for the first time in 2018, and plans to participate in the next cycle of ICILS, which is scheduled for 2023.

PISA — Program for International Student Assessment
PISA is an international assessment that measures 15-year-old students' reading, mathematics, and science literacy every 3 years. First conducted in 2000, the major domain of study rotates between reading, mathematics, and science in each cycle. PISA also includes measures of general or cross-curricular competencies, such as collaborative problem solving. By design, PISA emphasizes functional skills that students have acquired as they near the end of compulsory schooling. PISA is coordinated by the Organization for Economic Cooperation and Development (OECD), an intergovernmental organization of industrialized countries, and is conducted in the United States by NCES. Data collection for the most recent assessment occurred in fall 2022. Results will be released in December 2023.

TALIS — Teaching and Learning International Survey
TALIS is a survey about teachers, teaching, and learning environments. TALIS is composed of two questionnaires—one for teachers and one for their principals—that ask questions about respondents’ backgrounds, work environments, professional development, and beliefs and attitudes about teaching. TALIS is unique because it is the only comparative international education study that collects data on nationally representative samples of teachers and principals and provides key information on how they and their working and learning environments compare internationally. The core target population in TALIS is ISCED* level 2 (lower secondary) teachers and school principals. ISCED level 2 corresponds to grades 7, 8, and 9 in the United States. TALIS was first administered in 2008 and then in 2013 and 2018. TALIS is coordinated by the Organization for Economic Cooperation and Development (OECD), an intergovernmental organization of industrialized countries, and is conducted in the United States by NCES. The United States first participated in the 2013 cycle. The next cycle of TALIS is scheduled for 2024.

PIAAC — Program for the International Assessment of Adult Competencies

PIAAC is an international study for measuring, analyzing, and comparing adults’ basic skills. The assessment focuses on the basic cognitive and workplace skills needed for individuals to participate in society and for economies to prosper. Data from PIAAC is meant to help countries better understand their education and training systems and the distribution of these basic skills across the adult working-age population. PIAAC is intended to be administered at least once a decade. PIAAC is coordinated by the Organization for Economic Cooperation and Development (OECD), an intergovernmental organization of industrialized countries, and is conducted in the United States by NCES. Cycle I of PIAAC measured literacy, numeracy, and digital problem solving skills. It was first conducted in 2011 and the same survey instruments were administered twice more through 2017. In total, 39 countries participated in PIAAC in Cycle I (2011-17). Cycle II of PIAAC, with revised survey instruments, was conducted from 2022 to 2023. Thirty-one countries participated in Round 1 of Cycle II of PIAAC. In Cycle II, digital problem-solving was replaced by adaptive problem-solving (APS), which measures the ability to achieve one’s own goals in a dynamic situation in which a method for reaching a solution is not directly available.

* ISCED stands for the International Standard Classification of Education. Details on the ISCED classification system can found at


The United States participates in international studies primarily for two reasons:

  • to learn about the performance of U.S. students and adults in comparison to their peers in other countries; and
  • to learn about the educational and work experiences of students and adults in other countries.
Student assessments are a common feature of school systems that are concerned about accountability and ensuring students’ progress throughout their educational careers. National or state assessments enable us to know how well students are doing in a variety of subjects and at different ages and grade levels compared to other students nationally or within their own state. International assessments, on the other hand, offer a unique opportunity to benchmark our students' performance to the performance of students in other countries. Similarly, international assessments of adult literacy enable us to compare U.S. adults with their international peers on literacy skills that support productive adult lives in the workplace and society.

International assessments of students also enable countries to (1) learn from each other about the variety of approaches to schooling; and (2) identify promising practices and policies to consider in their schools. International assessments of adults enable research on the correlates between adults’ work and educational experiences and their skill levels within countries and cross-nationally.


Development and Administration

There are three main components in the development of test and survey questions:
  1. Test and survey questions for each study are first developed through a collaborative, international process.
    For each study, an international subject area expert group is convened by the organization conducting the study. This expert group drafts a framework (the outline of the topics and skills that should be assessed or surveyed in a particular domain), which reflects a multinational consensus on the assessment and survey of a subject area. Based on the framework, national representatives and subject matter specialists develop the test and survey questions. National representatives from each country then review every item to ensure that each adheres to the internationally agreed-upon framework. While not every item may be equally familiar to all study participants, if any item is considered inappropriate for a participating country or an identified subgroup within a country, that item is eliminated.
  2. Test and survey items are field-tested before they are used or administered in the full-scale study.
    Before the administration of the study, a field test is conducted in the participating countries. An expert panel convenes after the field test to review the results and look at the items to see if any results were biased due to national, social, or cultural differences. If such items exist, they are not included in the full study. Only after this thorough process, in which every participating country is involved, are the actual items administered to study participants.
  3. There is an extensive translation verification process.
    All participating countries are responsible for translating the assessment or survey into their own language or languages, unless the original items are in the language of the country. All countries identify translators to translate the source versions into their own language. External translation companies independently review each country's translations. Instruments are verified twice, once before the field test and again before the main data collection. Statistical analyses of the item data are then conducted to check for evidence of differences in performance across countries that could indicate a translation problem. If a translation problem with an item is discovered in the field test, it is removed for the full study. Since the items for TIMSS, ICILS, PIRLS, PISA, PIAAC, and TALIS are provided to countries in English, the United States does not need to translate the assessments but does adapt the international English versions to U.S. English when necessary and appropriate.
A nationally representative sample of the target population in each participating country responds to each study. In the case of ICILS, PIRLS, PISA, and TIMSS, the sample is drawn to be representative of students at the designated age or grade level. Teachers of selected students may also be sampled to participate, and school surveys are also conducted for each of these studies. In the case of PIAAC, the sample is drawn to be representative of persons 16 to 65 years old living in households1. In the case of TALIS, the sample is drawn to be representative of teachers.

The international organization that conducts each study verifies that all participating countries select a nationally representative sample. To ensure comparability, target grades, ages, or populations are clearly defined. For example, TIMSS countries participating in the study at the eighth-grade level sample students in the grade that corresponds to the end of 8 years of formal schooling, providing that the mean age of the students at the time of testing is at least 13.5 years.

Not all selected respondents choose to participate in the studies, and some respondents, such as those with cognitive or physical disabilities, may not be able to participate. Thus, the sponsoring international organizations check each country’s participation rates and exclusion rates to ensure they meet the target rates established for reporting the country’s results.

1 PIAAC U.S. national sample has an additional sample of 66-74-year-olds.
The short answer is that procedures for the administration of the international studies are standardized and independently verified.

The international organizations that conduct international studies require compliance with standardized procedures. Manuals are provided to each country that specify the standardized procedures that all countries must follow in all aspects of sampling, preparation, administration, and scoring. To further ensure standardization, independent international quality control monitors visit a sample of schools (or households in the case of PIAAC) in each country. In addition, each country organizes its own quality control monitors to visit an additional number of schools. Results for countries that fail to meet the international requirements are footnoted with explanations of the specific failures (e.g., "only met guidelines for sample participation rates after substitute schools were included"), are shown separately in the international reports (e.g., listed in a separate section at the bottom of a table), or are omitted from the international reports and datasets (as happened to the Netherlands' PISA results in 2000, the United Kingdom's PISA results in 2003, and Morocco's TIMSS 2007 results at grade 8).
In the United States, participation by respondents to international studies is voluntary. To our knowledge, no countries require all schools and students to participate in ICILS, PIRLS, PISA, or TIMSS. However, some countries give more prominence to these studies than do others.

To better measure the knowledge and skills required for success in the 21st century, all of the international studies in which the United States participates through NCES have transitioned to a digitally based format. In this format, participants respond to assessment or survey questions using a tablet or computer.

The transition to digitally based assessments (DBAs) allows:

  • better measurement across the assessment frameworks;
  • the possibility of adaptive assessments, which allow more accurate measures of performance at the top and bottom of the proficiency scale; and
  • more innovative ways to measure cognitive processes, including using interactive tasks, measuring timing, and recording the processes involved in responding.

Transition of International Large-Scale Education Studies to Digitally Based Assessments and Surveys

Study First Year of Digitally Based Components Digitally Based Implementation Details
TALIS 20081 TALIS administers online teacher and principal questionnaires.
PIAAC 2011 In 2011, PIAAC assessed adult literacy and numeracy using paper-based or computer-based assessments. The problem solving in technology-rich environments component was only computer-based. Interviewers administered the background questionnaire (BQ) and entered the participant’s responses into study laptops. In 2023, all components are only tablet-based.
PISA 2012 In 2012, PISA administered optional DBA assessments in mathematics, reading, and problem solving. In the 2015 cycle, the assessments for all domains were administered online for students. PISA administers online curriculum, school, teacher, and student questionnaires as well.
ICILS 20132 ICILS is a computer-based international assessment of eighth-grade students' computer and information literacy. Surveys of students, schools, and teachers are also administered online.
PIRLS 2016 In 2016, in addition to the paper-based PIRLS assessment, a subset of education systems administered ePIRLS, an innovative computer-based assessment of online reading. PIRLS administered online curriculum, school, and teacher questionnaires during this cycle. In 2021, PIRLS was administered as an entirely digital assessment referred to as digitalPIRLS, which included both the traditional PIRLS assessment in digital format as well as the interactive ePIRLS items. For the first time, the student questionnaire was also administered digitally.
IELS 2018 Children interact with tablet computers in activities to measure pre-literacy, pre-numeracy, self-regulation, and social emotional (empathy and trust) skills. Surveys of teachers and parents are also administered online.
TIMSS 2019 In 2019, for both the fourth and eighth grades, TIMSS administered eTIMSS, where mathematics and science items were administered via computers or tablets. During the 2019 cycle, all questionnaires (curriculum, school, teacher) were administered digitally, except for the student questionnaire. Beginning in 2023, all components of TIMSS will be administered digitally.
1 The United States did not participate in the 2008 cycle of TALIS; it first participated in the 2013 cycle.
2 The United States did not participate in the 2013 cycle of ICILS; it first participated in the 2018 cycle.

Issues of Validity and Reliability

The answer varies from study to study. Some studies, like TIMSS and PIRLS, are curriculum-based and are designed to assess what students have been taught in school using multiple-choice and open-ended (or short answer) test questions. Other studies, like PISA and PIAAC, are "competency" assessments, designed to measure performance in certain skill areas at a broader level than the school curriculum.
The fact that education systems are different across countries is one of the main reasons we are interested in making cross-country comparisons. However, these differences make it essential to carefully define the target populations to be compared so that the comparisons will be as fair and valid as possible. For studies that focus on students, depending in large part on when they first start school, students at a given age may have less or more schooling in different countries and students in a given grade may be of different ages in different countries. In every case, detailed information on the comparability of the sampled populations is published for review and consideration.

For PIRLS, the target population represents students in the grade that corresponds to 4 years of formal schooling, counting from the first year of schooling as defined by the International Standard Classification of Education (ISCED) Level 1. This corresponds to fourth grade in most countries, including the United States. This population represents an important stage in reading development.

In TIMSS, the two target populations are defined as follows: (1) all students enrolled in the grade that corresponds to 4 years of formal schooling—fourth grade in most countries—providing that the mean age at the time of testing is at least 9.5 years; and (2) all students enrolled in the grade that corresponds to 8 years of formal schooling—eighth grade in most countries—providing that the mean age at the time of testing is at least 13.5 years. For example, at grade 4 in 2007, only England, Scotland, and New Zealand included students who had 5 years of formal schooling at the time of testing. At grade 8, England, Malta, Scotland, and Bosnia and Herzegovina included students who had 9 years of formal school at the time of testing. In addition, at grade 8, the Russian Federation and Slovenia included some students who had less than 8 years of formal schooling. However, in all of these cases, the assessed students were of comparable average age to those participating in other countries.

Another approach, used in PISA, is to designate the target population as students of a particular age (15 years in PISA), regardless of grade. Both approaches are suited to addressing the particular research questions posed by the assessments. The focus of TIMSS and PIRLS is on content as commonly expected to be taught in classrooms, while PISA emphasizes the skills and knowledge that students have acquired throughout their education both in and out of school.
Each country has different population characteristics, but the point of international studies is to measure as accurately as possible the levels of achievement or proficiency of each participating country’s target population. Differences in the levels of achievement or proficiency among students or adults in different countries may be associated with high variations in respondent characteristics, but they may also be due in part to differences in curriculum, teacher preparation, and other educational or societal factors. Using data from the respondent surveys can support analyses of the potential factors that may contribute to achievement in different countries.
Countries cannot independently select the students who will take the test. Students are sampled, but the sampling of schools and students is carefully planned and monitored by the sponsoring international organizations.

Sampling within countries proceeds as follows:
A sample of schools in each country is selected randomly from lists of all schools in the country that have students in the particular grade or of the particular age to be assessed. Samples for each country are verified by an international sampling referee. Once the sample of schools has been selected, each country must contact the schools in the sample to solicit their participation in the assessment. Countries are not allowed to remove schools from, or add schools to, the list; doing so can result in the exclusion of their data from the reports. Every study establishes response rate targets of selected schools (and students) that countries must meet in order to have their data reported. If the response rate target is not met, countries may be able to assess students from substitute schools following international guidelines. For example, PIRLS and TIMSS guidelines specify that substitute schools be identified at the time that the original sample was selected by assigning the two schools neighboring the sampled school in the sampling frame as substitutes. If the original school declines to participate, the first of two substitute schools is contacted to participate. If it declines, the second substitute school is contacted. If it also declines, no other substitute school may be used. If one of the two substitute schools accepts, there are still several constraints on their participation in order to prevent bias. If participation levels, even using substitute schools, still fall short of international or national guidelines, a special nonresponse bias analysis is conducted to determine if the schools that did not participate differ systematically from the schools that did participate. If the analysis does not show evidence of bias, the data for a country may still be included in the reporting of results for the international assessment, but the problem of participation rates is noted.

Once a sample of schools agrees to participate, the schools are asked to provide a list of all students of the target age or a list of a particular kind of class (for example, all grade 4 classrooms) within the school. From those lists, a group or whole class of students is then randomly selected for the assessment. No substitutions for the students randomly selected are allowed. However, some individual students may be excluded. Each study establishes a set of guidelines for excluding individual students from assessment. Typically, if a student has a verifiable cognitive or physical disability, he or she can be excluded from assessment. However, all student exclusions (at the school level and within schools) cannot exceed established levels and are reported in international publications. For example, the sampling standards used in PISA permit countries to exclude up to a total of 5 percent of the relevant population for approved reasons. In the United States, the overall exclusion rate in PISA 2018 was 3.8 percent.

Exclusions can take place at the school level (e.g., excluding very small schools or those in remote regions) and the student level. While accommodations are provided to students specific to each study, in some cases students may be excluded if they are functionally disabled, intellectually disabled, or have insufficient language proficiency. This determination is made on the basis of information from the school in conjunction with the allowed accommodations, although the contractors implementing the study also look out for ineligible students who may make it through the screening process. Students cannot be excluded solely because of low proficiency or normal discipline problems.

Reported Results

No. The assessment methods used in international assessments only produce valid scores for groups, not individuals.

No. The U.S. data are typically representative of the nation as a whole but not of individual states. Drawing a sample that is representative of all 50 individual states would require a much larger sample than the United States currently draws for international assessments, requiring considerable amounts of additional time and money.

A state may elect to participate in an international assessment as an individual jurisdiction, in which case a sample is drawn that is representative of that state. State participation in international assessments provides them with the opportunity to assess the comparative international standing of their students' achievement and skills and to view their curriculum and instruction in an international context. To date, several states have participated in TIMSS, PIRLS, and PISA that way. For a list of states that have participated in each assessment, please view the country lists for TIMSSPIRLS, and PISA.

Separately, the U.S. PIAAC 2012/2014 sample and the U.S. PIAAC 2017 sample do not have enough respondents to produce accurate estimates of adults’ skills at the state or county level. However, using a technique called small area estimation (SAE), NCES was able to develop a model that combines the 2012/2014 and 2017 samples to produce estimates of adults’ skills for all U.S. states and counties. These estimates are available in the U.S. PIAAC Skills Map: State and County Indicators of Adult Literacy and Numeracy

Scores can be compared from one round of an assessment to another round of the same assessment (e.g., TIMSS 1999 to TIMSS 2007). However, due to differences in frameworks, target populations, and other factors, they typically cannot be directly compared from one study to another (e.g., TIMSS to PISA or NAEP) without special studies to link the different assessments. To help readers understand the similarities and differences between the assessments, over the years NCES has developed a series of cross-study comparisons that provide detailed information on the purposes, target populations, reporting levels, and content assessed through the different studies.
No. The assessments for each grade are scaled separately, so the scores cannot be directly compared in a meaningful way. Only scores from different rounds of the same assessment (e.g., 2003 TIMSS grade 4 and 2007 TIMSS grade 4) can be compared.

At times, different assessments report different findings for the same subject. One obvious factor to consider when examining findings across assessments is that the grade or age levels of the students assessed may differ. Another factor is that studies also differ in the specific subject matter or skills emphasized, (e.g., reading, mathematics, science). To help readers understand the similarities and differences between the assessments, NCES has developed a series of cross-study comparisons that provide detailed information on the purposes, target populations, reporting levels, and content assessed through the different studies.

An additional difference between assessments that can affect the findings in terms of the U.S. position relative to other countries is the groups of countries involved in a study. The United States may appear to perform better or worse depending on the number and competitiveness of the other participating countries.

There are certain demographic characteristics that are not meaningful across countries. Race/ethnicity is one of these. In the United States, race and ethnicity are highly correlated with education and socioeconomic status, which makes them meaningful categories for analysis. While that may be true in other countries, the racial and ethnic categories or demographic priorities for analyses vary from country to country. Each country has the option to add its own national items to the international surveys. Since they are national items, results will only exist for that country. In the United States, one of the national items generally added to international surveys asks about respondents’ race and ethnicity.

Study-specific FAQs

To view frequently asked questions related to ICILS, please visit
To view frequently asked questions related to IELS, please visit
To view frequently asked questions related to PISA, please visit
To view frequently asked questions related to PIRLS, please visit
To view frequently asked questions related to TALIS, please visit
To view frequently asked questions related to TIMSS, please visit
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International Exchange Programs and Foreign Study

Basic Facts

The Institute of International Education (IIE) provides detailed information on U.S. students studying in foreign postsecondary institutions and foreign students studying in U.S. colleges and universities. Details on IIE's Open Doors project can be found at
The U.S. Department of Education does not review or determine the equivalency of foreign degrees to U.S. degrees. More information on the process involved in determining the equivalency of degrees can be found at

Information for Students Seeking to Study in the United States

Go to for detailed information on all that is involved with studying in the United States as a foreign student.
NCES offers an online tool that assists in searching for colleges and universities in the United States by a number of factors, such as location, program or major, tuition costs, and student enrollment size. To visit the NCES College Navigator, go to
Generally, if you have a "green card" (in other words, if you are a permanent resident alien), you will be considered an "eligible noncitizen" and will be able to get federal student aid if you meet the other basic eligibility criteria. Full details of which immigration statuses make you an eligible noncitizen are at
Go to the Federal Student Aid site at and use the “Federal School Code Search.” Schools that are qualified to disburse U.S. federal student aid are included in this list.
The U.S. Department of Education does not accredit educational institutions and/or programs. However, the Secretary of Education is required by law to publish a list of nationally recognized accrediting agencies that the Secretary determines to be reliable authorities as to the quality of education or training provided by the institutions of higher education and the higher education programs they accredit.

The U.S. Secretary of Education also recognizes state agencies for the approval of public postsecondary vocational education and nurse education. For more information, go to
Go to for the Federal School Code List. Students can enter codes from this list onto the Free Application for Federal Student Aid (FAFSA) to indicate which postsecondary schools they want to receive their financial application results.

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