In 2014, the Bill & Melinda Gates Foundation launched two initiatives to support the spread of personalized learning. The Foundation asked CRPE to observe how participating districts and regions were beginning to define and pursue personalized learning and what grantees were learning about how to innovate at scale. Drawn from 450 interviews with 300 teachers, principals, superintendents, and central office staff in 17 cities; classroom observations and student focus groups in 39 schools; and surveys of 908 teachers from the initiatives, the early challenges underscore the difficulty of innovating inside the current system. CRPE suggests four things leaders must do to build a strategic system to support innovation at scale.