High school capstone courses—culminating educational experiences for seniors as they conclude their formal high school education—have become increasingly popular across the nation, particularly in New England. The STEMStarter Capstone was designed to help Connecticut high schools meet new accreditation standards from the New England Association of Schools and Colleges (NEASC) and graduation requirements that include a mastery-based learning project. Standard 2 of the NEASC 2020 Standards (2018) for school accreditation states: “Students are active learners and have the opportunity to lead