The Responsive Classroom Efficacy Study (RCES) is a randomized controlled trial examining the efficacy of the Responsive Classroom® Approach. The Responsive Classroom® Approach, an intervention developed by the Northeast Foundation for Children, is designed to integrate social and academic learning and improve the capacity of teachers to manage their classrooms effectively. RCES involved 24 schools and data collection began in January, 2008. It was designed as a three year longitudinal study; children and their teachers were followed from grades three through five with a special emphasis on the extent to which the Responsive Classroom® Approach related to classroom quality during mathematics instruction and ultimately, children’s math achievement. This work was funded by the U.S. Department of Education, Institute for Education Sciences through a Teacher Quality Mathematics grant awarded to Sara Rimm-Kaufman, Xitao Fan, and Robert Berry. Contact Lab Managing Director Julie Thomas at jbt4u (at) virginia (dot) edu for more information.