The "What Works Clearinghouse" guidelines for high-quality professional development were used to develop a Tell, Show, Try, and Apply (TSTA) method of training. This method was used to train teachers to align instruction to grade-level content for students with severe developmental disabilities. A total of 193 teachers of students who participate in alternate assessment based on alternate achievement standards from three states participated in the first 2 days of training. A subset of 37 teachers participated in a 3rd day of training and submitted products from classroom applications. The impact of the TSTA training was evaluated to determine its effect on teachers' instructional fidelity across three content areas (e.g., English language arts [ELA], mathematics, science) with their own students. In addition, generalization to new academic content aligned to grade-aligned standards developed by the teachers was taken. Results indicated that the professional development was effective not only in increasing teachers' knowledge of alignment but also grade-aligned instruction with generalization across content. Future research questions and practical application also are discussed. (Contains 2 tables and 3 figures.)