Many teachers are underprepared to meet the needs of students with disabilities. Most have insufficient training and field experiences from their preparation programs, and once they begin teaching, they often lack collaborative professional learning about supporting students with disabilities. This article describes s how a multidisciplinary team across teacher preparation and research communities set out to develop and test guidance and support materials, to help general education teachers support elementary students with mathematics disabilities. The project engaged dozens of experts from both general education and special education in collaborative work. It then examines the recommendations learned from the project: (1) Build bridges across general and special education; (2) Target focal instructional practices; (3) Build foundational knowledge about students and content; (4) Illustrate what the focal practice looks like; and (5) Build in time for practice and immediate, nonevaluative feedback.