The conventional approach to school implementation involves different sets of schools in designing, developing, and testing an innovation and yet another set of schools involved in implementation at scale. Decades of research suggest that this approach has yielded inconsistent and often disappointing improvements for schools most in need. More recent scholarship on scaling school improvement suggests these should activities should be integrated, although this presents challenges in how we evaluate implementation in particular schools. This paper presents a framework to conceptualize implementation when design, implementation, and scaling up are integrated activities. [This article was published in "Peabody Journal of Education," v92 n5 p589-608 2017 (EJ1157621).]