This study presents findings from an evaluation of the Developmental Designs classroom management approach and professional development model during its first year of implementation across 22 middle schools in a large, Midwestern school district. The impact of this professional development model on teaching and learning as related to participants' levels of competence, confidence, and implementation were examined. Evidence-based methods utilizing a quasi-experimental design produced data on 2 levels, known as Developmental Designs 1 (DD1) and Developmental Designs 2 (DD2). Participants included 317 DD1 and 43 DD2 teachers, staff, and administrators. Existing participant demographic data were obtained unobtrusively from the school district. Survey questionnaires detailing the quality of the professional development received, confidence in utilizing strategies, and levels of classroom implementation were used to collect perceptual data from participants. These data indicate an overall high degree of satisfaction with the Developmental Designs approach and professional development model. However, the second year of DD2 training resulted in significantly higher teacher confidence and classroom implementation levels. This finding is important to the professional development knowledge base in that it documents the need for a minimum of 2 year's training and classroom use to achieve significant improvement in teachers' confidence in and implementation of new strategies for classroom management. (Contains 12 tables.)