The purpose of this study was to investigate the impact of a hands-on science curriculum, which integrates mathematics and supports English language development, on third-grade students' mathematics achievement--specifically the measurement subscale of the statewide assessment. The data drew from a larger five-year research and development project consisting of reform-based science curriculum units and teacher workshops designed to promote effective science instruction while integrating mathematics and supporting English language development. The third-grade curriculum places a strong emphasis on measurement skills in the context of science inquiry. The third-grade students' performance on the measurement subscale of the statewide mathematics assessment in the treatment schools was compared with that of comparison schools using a hierarchical linear model. Students at the treatment schools performed significantly higher than students at the comparison schools. The results provide evidence that an integrated approach to mathematics and science instruction can benefit diverse student groups. (Contains 7 tables and 4 figures.)