To prevent and address students' problem behaviors and support their learning, the Department of Education and many states have promoted the use of multi-tiered systems of support for behavior (MTSS-B). This study evaluated one promising, intensive program of MTSS-B training and technical assistance. The MTSS-B approach seeks to change the school learning environment by consistently teaching and reinforcing good behavior for all students and identifying and providing supplemental support to students who need it. About 90 elementary schools were randomly assigned either to participate in the program or to continue with their usual strategies for supporting student behavior. The study compared student and teacher experiences in the two sets of schools to measure the effectiveness of the program. [For the appendix, see ED620902. For the Study Highlights, see ED620901.]