The School of One initiative in New York City schools (since spun out nationally from the school district as New Classrooms*) was always an initiative to watch for a few reasons. It was bold and leading edge and it was happening inside a school district. At five it offers some lessons and two of the players behind it are reflecting on them. You can follow along here.
*New Classrooms funded Bellwether to analyze policy plays to expand and improve the quality of personalized learning initiatives (pdf).