Abstract
Project Achieve is a professional development (PD) project that utilizes teacher leaders (TLs), former teachers who have been reassigned to provide school‐based mentoring, instruction, lesson plan assistance and modelling of lessons for urban middle school teachers. A primary goal of Project Achieve is to evaluate the extent to which TLs were able to increase teaching skill to such an extent that it positively impacted student learning. The results of this comparative case study reveal that Project Achieve was successful in improving teaching performance and increasing student achievement.