Inquiry-based science interventions aim to improve students' science proficiency by helping them understand scientific processes. In these interventions, students conduct hands-on investigations of science concepts and everyday phenomena, construct explanations for what they observe, consider alternative explanations, and communicate and justify their proposed explanations. Because implementing inquiry-based science instruction is challenging, the Smithsonian Science Education Center (SSEC) developed "Leadership and Assistance for Science Education Reform" (LASER), a program designed to build capacity for effectively implementing inquiry-based science curricula in schools and districts. When participating in LASER, school or district teams attend leadership development institutes to plan the implementation of inquiry-based science curricula. This What Works Clearinghouse (WWC) intervention report, part of the WWC's Primary Science topic area, explores the effects of LASER on science achievement. The WWC identified two studies of LASER. One of these studies meets WWC standards. The evidence presented in this report is from one study of the effects of LASER on students, including 44% Hispanic, 31% White, 19% Black, 3% American Indian/Alaska Native, and 2% Asian students. LASER was implemented in grade 3 and 6 classrooms at the start of the study with outcomes measured after 3 years of implementation when students were in grades 5 and 8. Study schools were located in 16 urban, suburban, and rural school districts in New Mexico, North Carolina, and Texas. [For the Intervention Brief, see ED614850. For the Intervention Snapshot, see ED614849.]