A third attempt by educators to compare achievement in mathematics and science across nations. Although criticized by some as lacking reliability, it is the largest, most recent, and best-controlled study of its sort. TIMSS administered tests to students in 26 countries at grade 4 and 41 countries at grade 8. Depending on the specific test, it was administered to up to 21 countries at the Final Year of Secondary School. (It is called the Final Year because, in many instances, it does not respond to 12th grade in the United States.)