This protocol guides the review of research that informs the What Works Clearinghouse (WWC) Primary Science (PS) intervention reports. The protocol is used in conjunction with the "WWC Procedures Handbook (version 4.0)" and the "WWC Standards Handbook (version 4.0)." Large numbers of students lack proficiency in science, and students from different ethnic and socioeconomic groups show disparities in science achievement. Science knowledge and skills are important for both academic and workplace success, and a number of interventions aim to improve student science achievement. This review focuses on science interventions used in kindergarten through grade 8 and designed to affect students' science achievement. The following research questions guide this review: (1) Which interventions are effective at increasing the learning of science content, processes, and skills for students in kindergarten through grade 8?; and (2) Are some primary science interventions more effective for certain types of students, particularly those who are members of traditionally underrepresented groups in science?