This research examined the impact of the first-year implementation of an instructional intervention to promote achievement and equity in science and literacy for culturally and linguistically diverse elementary students. The research addressed three areas: (a) overall science and literacy achievement, (b) achievement gaps among demographic subgroups, and (c) comparison with national (NAEP) and international (TIMSS) samples of students. The research involved 1,523 third- and fourth-grade students at six elementary schools in a large urban school district. Significance tests of mean scores between pre- and posttests indicate statistically significant increases on all measures of science and literacy at both grade levels. While achievement gaps widened with third graders on some of the measures, the gaps tended to narrow with fourth graders. The results based on item-by-item comparisons with NAEP TIMSS samples of students indicated overall positive performance of the students in the research at the end of the school year.