Implemented was a 45-minute per day Primary Science IDEAS intervention in grades 1-2 integrating reading and writing within science instruction in a multi-year study conducted in 8 experimental and 9 control schools. Results found a significant direct achievement effect in grades 1-2 on both the Iowa Tests of Basic Skills (ITBS) Science and Reading. In addition, the direct effect of the intervention in grades 1-2 also resulted in significant achievement transfer from grades 1-2 to grade 3 on both the ITBS Science and Reading. Discussed are policy implications of the findings for increasing instructional time allocated to science in grades 1-2 and expanding the focus of grade 1-2 student achievement assessment to include content-area learning.