In addition to the following questions about TIMSS, more FAQs about international assessments are available at: http://nces.ed.gov/surveys/international/faqs.asp.
The TIMSS TIMSS results at grade 8, the grade closest to the age of PISA students, showed U.S. average scores higher than the TIMSS scale average in both mathematics and science. In PISA 2006, the average scores of U.S. 15-year-old students were below the Organization for Economic Cooperation and Development (OECD) average—the average score of students in the 30 OECD countries. Such differences are difficult to compare because, while both TIMSS and PISA measure the mathematics and science achievement of students, they do so for different sets of students, in different ways, and in different sets of countries.
TIMSS focuses on the mathematics and science achievement of students in the fourth and eighth grades, and selects whole classrooms of students for this purpose. In contrast, PISA aims to assess the mathematics and science literacy of students near the end of their compulsory schooling, at age 15. These students range across several grades in most countries.
TIMSS draws its content directly from the school curriculum and is designed to assess how well students have learned what they have ostensibly been taught. TIMSS emphasizes the links between achievement, mathematics and science curricula, and classroom practices. In contrast, PISA’s intent is to measure a "yield" of the skills and competencies accumulated and applied in real-world contexts by students at age 15. PISA emphasizes the mastery of processes, understanding of concepts, and application of knowledge. It draws not only from school curricula but also from learning that may occur outside of school. PISA does not explicitly examine mathematics and science curricula and classroom practices, though it does collect school information, including school background information and information on school practices and resources.
Both assessments cover much of the world and include key economic partners and competitors, but there is only partial overlap between the sets of participating countries. For instance, only 26 of the 48 countries that participated in TIMSS 2007 at grade 8 participated in PISA 2006. PISA focuses on the 30 OECD-member countries, treating the non-OECD jurisdictions separately. Comparing the PISA countries with the TIMSS countries highlights the different sets of countries participating in each study. For example, European countries make up about two-thirds of all PISA countries but only one-third of TIMSS countries, and Middle-Eastern countries make up about 3 percent of all PISA countries but 25 percent of TIMSS countries. About 25 percent of TIMSS countries participate in PISA, and about one-half of PISA countries are in TIMSS as well.