Produced by a CADRE work group of NSF-supported researchers and developers, this practice brief makes a case for substantive partnerships between STEM education R&D projects and districts and schools.  Despite leading a wide variety of projects, the authors have found that these kinds of partnerships can enhance the quality, relevance, and usability of project outcomes, with implications for sustained and scaled use of project knowledge.  The brief summarizes what the authors have learned about creating and maintaining partnerships, as well as potential pitfalls and challenges.  Along with practical strategies, the authors provide examples from project experience.