To identify the mathematics and science content knowledge and understandings associated with the Third International Mathematics and Science Study (TIMSS) empirically derived benchmarks of performance for the 4th and 8th grades - the 90th, 75th, 50th, and 25th
international percentiles of performance - the TIMSS 1995 International Study Center conducted an in-depth analysis of achievement on the TIMSS 4th- and 8th-grade mathematics and science tests. Sets of items that students reaching each international benchmark could answer correctly were identified. Two 10-member panels of subject-matter specialists were convened to scrutinize the sets of items and describe student proficiency at each level. By articulating performance at the TIMSS international benchmarks, "world class" achievement has been defined. Together, the benchmark descriptions and the percentages of students in each country reaching each international benchmark show the strengths and weaknesses of 4th and 8th graders in the TIMSS countries.