Research on science achievement disparities by gender and race/ethnicity often neglects the beginning of the pipeline in the early grades. We address this limitation using nationally representative data following students from Grades 3 to 8. We find that the Black-White science test score gap (-1.07 SD in Grade 3) remains stable over these years, the Hispanic-White gap narrows (-0.85 to -0.65 SD), and the Asian-White Grade 3 gap (-0.31 SD) closes by Grade 8. The female-male Grade 3 gap (-0.23 SD) may narrow slightly by eighth grade. Accounting for prior math and reading achievement, socioeconomic status, and classroom fixed effects, Grade 8 racial/ethnic gaps are not statistically significant. The Grade 8 science gender gap disappears after controlling for prior math achievement.