and Hispanic students of all ages remained unchanged. In 1999, boys out-performed girls in science at ages 13 and 17, but not at age 9. Among 17-year-olds, the score gap between boys and girls has narrowed since 1969 (Campbell, Hombo, and Mazzeo, 2000).

Like the long-term trend NAEP, the NAEP science achievement test focuses primarily on mastery of subject matter. Between 1996 and 2000, the average score of 12th grade students on this test declined from 154 to 150 (a small but statistically significant amount), while the scores of 4th grade and 8th grade students remained unchanged (National Center for Education Statistics, 2001a). Student performance on the NAEP science achievement test also varied by race and by students’ socioeconomic status. In both 1996 and 2000, the average score for white students was higher than the average for black and Hispanic students. Students of lower socioeconomic status, as indicated by their eligibility for free or reduced-price meals, had lower average NAEP science scores than students from more wealthy families (National Center for Education Statistics, 2001b).

Results of International Comparative Tests

Results of international comparisons provide additional insight into the science knowledge of U.S. high school students. TIMSS assessed the science performance of 8th graders in the United States and many other countries in 1995, 1999, and 2003. Over that time period, U.S. 8th graders improved their average science performance slightly, both in comparison with the earlier cohorts of 8th graders and relative to the 44 other countries that participated in the studies (Gonzales et al., 2004). The average scale score in science increased from 513 in 1995 to 527 in 2003, placing the United States well above the international average of 473 among all 8th graders in all participating nations.

Like the framework of the NAEP science achievement test, the TIMSS framework includes both a range of science subject matter and also student abilities related to scientific inquiry and investigations. However, with fewer performance tasks than the NAEP science achievement test, TIMSS may be more limited in its capacity to measure student attainment of the other goals of laboratory experience, besides mastery of subject matter (Owen, 2005).

Results from another international comparative test, PISA, suggest U.S. high school students have not increased their science achievement. In 2000 and 2003, 15-year-old students in many countries took two-hour PISA tests that focused primarily on reading (in 2000) and mathematics (in 2003) and also included some items related to scientific literacy. The U.S. scientific literacy score was below the average among OECD countries in 2000 and in 2003, and there was no measurable change in U.S. students’ scores between the two years (Lemke et al., 2004). The PISA science test framework includes



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