This study investigated the impact of a summer institute with follow-up coaching (treatment) versus no professional development (control) on middle and high school teacher and student science practice outcomes. Treatment teachers participated in a 2-week summer institute that used evidence-based professional development practices followed by remotely delivered instructional coaching led by project-based science coaches over 6-8 weeks during the school year. Results from 124 teachers across 110 schools showed significant differences between treatment and control groups for teacher science practice knowledge, performance, beliefs, and self-efficacy and student science practice skills and self-efficacy. Teacher effect sizes for the combined summer institute plus coaching (treatment) across all dependent variables ranged from 0.67 to 1.37. Student comparisons showed higher science practice performance for the treatment group; effect sizes were 0.39 for high school and 0.34 for middle school. Results demonstrated significantly higher increases in student self-efficacy for the treatment compared to the control group, and this increased self-efficacy was sustained through the end of the school year. Results substantiate the value of combining coaching with a summer institute to support teacher growth and development, with the summer institute providing foundational knowledge and fostering teacher self-efficacy to effectively implement newly learned instructional practices. The coaching in turn built on that foundation and provided needed support for teachers to transfer knowledge and skills to classroom practice.