Effective professional development is considered the center of educational reform (Dilworth & Imig, 1995). It is critical for teacher growth and student achievement. When teachers are given the opportunity, via high-quality professional development, to learn new strategies for teaching to rigorous standards, they report changing their teaching in the classroom (Alexander, Heaviside, & Farris, 1998). To be effective, professional development should be based on curricular and instructional strategies that have a high probability of affecting student learning—and, just as important, students’ ability to learn (Joyce and Showers, 2002). The National Commission on Mathematics and Science Teaching for the 21st Century (2000) said that professional development should (1) deepen teachers' knowledge of the content being taught; (2) sharpen teaching skills in the classroom; (3) keep up with developments in the individual fields, and in education generally; create and contribute new knowledge to the profession; and (5) increase their ability to provide explicit feedback to students.