This paper explores the question of whether it is possible to design professional development programs for teachers that can significantly improve student test results and reduce the achievement gap for students. The Dayton (Ohio) Foundation and the Montgomery County (Ohio) Educational Service Center, sponsors of The Miami Valley Teacher/ Leadership Academy, answer this question with a resounding yes. Recent results indicate that the academy's two-year program, designed to provide professional development to help improve student test scores, not only succeeded in significantly improving the student proficiency mean score, but also considerably reduced the achievement gap for participating students. This paper includes two parts. First, the authors discuss how to measure the achievement gap and assess its changes in individual classrooms. Second, they report the findings of an original research project relative to affecting the achievement gap. (Contains 6 figures and 2 endnotes.)