Today the National Center for Education Statistics is releasing results on the performance of students in the United States on an international study, the Program for International Student Assessment (PISA). PISA is a system of international assessments that measures 15-year-old students’ performance in reading literacy, mathematics literacy, and science literacy every 3 years. PISA, first implemented in 2000, is sponsored by the Organization for Economic Cooperation and Development (OECD), an intergovernmental organization of 30 member countries.

PISA uses the terminology of "literacy" in each subject area to denote its broad focus on the application of knowledge and skills. For example, PISA seeks to assess whether 15-year-olds are scientifically literate, or to what extent they can apply scientific knowledge and skills to a range of different situations they may encounter in their lives. The target age of 15 allows jurisdictions to compare outcomes of learning as students near the end of compulsory schooling. PISA’s goal is to answer the question "what knowledge and skills do students have at age 15?" taking into account schooling and other factors that may influence their performance. In this way, PISA’s achievement scores represent a “yield” of learning at age 15, rather than a direct measure of attained curriculum knowledge at a particular grade level, because 15-year-olds in the United States and elsewhere come from several grade levels.

In the 2006 assessment, 57 education systems (called jurisdictions in the report, these were nearly all countries, but included subnational entities such as Hong Kong and Macao-China) participated in PISA, including all 30 OECD countries and 27 non-OECD jurisdictions. The United States has participated in all three administrations of PISA (2000, 2003, and 2006).

Each PISA data collection effort assesses one of the three subject areas in depth, even as all three are assessed in each cycle so that participating jurisdictions have an ongoing source of achievement data in every subject area. In this third cycle, PISA 2006, science literacy was the subject area assessed in depth. In 2009, PISA will focus on reading literacy, which was also assessed as the major domain in 2000.

The results presented here focus on the performance of U.S. students in the major subject area of science literacy as assessed in PISA 2006. Achievement in the minor subject area of mathematics literacy in 2006 and differences in achievement by selected student characteristics are also presented.

How PISA Was Conducted
PISA 2006 was a 2-hour paper-and-pencil assessment of 15-year-old students and a 30-minute student background questionnaire. Like other large-scale assessments, PISA was not designed to provide individual student scores, but rather national and group estimates of performance. PISA 2006 was administered between September and November 2006. The U.S. sample included both public and private schools, randomly selected and weighted to be representative of the nation. In total, 166 schools and 5,611 students participated in PISA 2006 in the United States. More information about how the assessment was developed and conducted is included in the technical notes of the U.S. report on PISA. An additional source of information will be the PISA 2006 technical report to be published by the OECD and scheduled for release in 2007.

U.S. Performance in Science Literacy

The PISA 2006 assessment measures student performance on a combined science literacy scale and on three science literacy subscales: identifying scientific issues, explaining phenomena scientifically, and using scientific evidence. PISA scores are reported on a scale that ranges from 0 to 1000 with a mean of 500 and a standard deviation of 100.

Performance on the Combined Science Literacy Scale
On the combined science literacy scale, U.S. 15-year-old students’ average score (489) was lower than the OECD average (500). The U.S. average score was lower than the average score in 16 of the other 29 OECD jurisdictions and 6 of the 27 non-OECD jurisdictions. The U.S. average score was higher than the average scores of students in 22 jurisdictions (5 OECD and 17 non-OECD).

Finland was the top scoring country in 2006. Among the G-8 countries, four (Canada, Germany, Japan and the United Kingdom) scored higher than the United States.

When comparing the science performance of the highest-achieving students, there was no measurable difference between the score of U.S. students at the 90th percentile compared to the average score at the 90th percentile among OECD countries. In 12 jurisdictions (9 OECD and 3 non-OECD), students at the 90th percentile scored higher than their counterparts in the United States.

In 2003, the U.S. average score in science literacy was 491, lower than the OECD average as well as the average scores in 18 countries (including 15 OECD countries). Note that because of changes in the instruments for science between 2003 and 2006, the U.S. science scores between these two years are not comparable.

Proficiency Levels
Along with scale scores, PISA 2006 also uses six proficiency levels (levels 1 through 6, with level 6 being the highest level of proficiency) to describe student performance in science literacy. An additional level (below level 1) includes students whose skills are not developed sufficiently to be described by PISA.

The United States had greater percentages of students at or below level 1 than the OECD average percentages on the combined science literacy scale. The percentages of U.S. students performing at the highest levels 5 and 6 were not measurably different from the OECD averages.

Performance of U.S. Students on the Science Literacy Subscales: Identifying Scientific Issues, Explaining Phenomena Scientifically, and Using Scientific Evidence
Although not the terms commonly used in schools, each of the sub-areas used in PISA has a relationship to the typical courses taught in U.S. schools. The concepts are the familiar ones of physics, chemistry, biological sciences, and Earth and space sciences. The processes are centered on the ability to acquire, interpret, and act on evidence such as describing scientific phenomena and interpreting scientific evidence. The sample items in the report show examples of what each subscale measured. PISA uses these sub-areas to evaluate the application of knowledge and skills to problems in a real-life context.

On two of the three subscales (explaining phenomena scientifically and using scientific evidence) U.S. 15-year-old students had lower scores than the OECD average score in 2006. Of the other 56 jurisdictions, students in 19 OECD and 6 non-OECD jurisdictions scored higher, on average, than U.S. students on the explaining phenomena scientifically subscale. The U.S. scores were also lower, on average, than 14 OECD and 6 non-OECD jurisdictions on the using scientific evidence subscale.

There was no measurable difference between the U.S. average score and the OECD average on the identifying scientific issues subscale. However, U.S. 15-year-old students scored lower, on average, than 18 jurisdictions (13 OECD and 5 non-OECD).

Differences in Performance by Selected Student Characteristics

Performance by Sex
While the OECD average was higher for males than females, U.S. male and female students’ scores did not differ measurably on the combined science literacy scale. In the United States, female students scored higher than male students on the identifying scientific issues subscale, while male students scored higher than female students on the explaining phenomena scientifically subscale. There was no measurable difference between the performance of U.S. male and female students on the using scientific evidence subscale.

Performance by Race/Ethnicity
Because racial and ethnic groups vary across countries, it is not possible to compare performance by race/ethnicity on international assessments. In the United States, students were asked whether they were of Hispanic origin and their race. Students who identified themselves as being of Hispanic origin were classified as Hispanic, regardless of race. Black students and Hispanic students scored lower, on average, on the combined science literacy scale than White students, Asian students, and students of more than one race. Hispanic students scored higher than Black students. White students scored higher than Asian students and were the only U.S. racial group to score higher than the OECD average.