Five years ago, a former high school principal named Brian Greenberg joined forces with an heir to the retail giant Gap, John Fisher, to start a fund to help scale promising charter schools.

This week the group, called Silicon Schools Fund, released a report reflecting on its efforts so far, which have supported 31 schools, 24 of which were brand new, with a total of $50 million. The bad news: They admit there isn’t yet enough hard evidence that personalized learning really works. The good news: There are plenty of positive signs, both when measuring students across standardized tests and when looking for signals of engagement. They suggest moving forward with what they call Urgent Patience.

EdSurge’s CEO, Betsy Corcoran, sat down with Greenberg to talk about the report, along with his colleague Caitrin Wright. Here are highlights from their conversation.