Policy Studies Associates (PSA) has evaluated the national demonstration of ExpandED Schools since the demonstration, supported by The Wallace Foundation and others, was launched in the 2011-12 school year in 10 schools in New York City, Baltimore and New Orleans. Over four years, the evaluation explored the approaches that participating schools took to adopting the ExpandED Schools model, in particular seeking to understand the conditions that support—or hinder—the implementation of an expanded day.