Like never before, today's classroom teachers routinely are being asked to collaboratively analyze student data, develop or implement new mandated curricula, and assess the effectiveness of these innovations. Ironically, few preservice preparatory or in-service professional development programs actively train classroom instructors in the use of team-based inquiry or collaborative data-driven problem solving. This article describes one in-service program focused on team-based inquiry and collaborative data-driven problem solving, in practice at public and charter schools in high-need communities in New York City.