Research has documented that skilled and highly effective teachers make a positive difference in student learning and achievement. Research has also shown that more time spent on quality professional development means more effective teaching. Hence, the National Middle School Association (NMSA) asserts that more research is needed that connects quality professional development to student learning outcomes. This article examines the results of a teacher leader training model entitled Project Achieve, which focuses on improving middle level teaching performance and student achievement. The teacher leader model was implemented at an urban middle school during the 2005-2006 academic year. The premise of Project Achieve is that when teachers are given opportunities to improve their teaching practice through on-site, personalized, professional development by teacher leaders, increased student learning follows naturally. (Contains 3 figures.)