This brief from the EdResearch for Action Design Principles Series examines how well-designed instructional coaching programs can improve teacher practice and student outcomes through individualized, intensive, and sustained support. Drawing on a 2018 meta-analysis of 60 causal studies, the brief highlights the potential impact of coaching, finding that the difference in effectiveness between coached and uncoached teachers was comparable to the difference between novice teachers and those with five to ten years of experience. The findings also emphasize the importance of coaches’ instructional expertise and trusting relationships with teachers, the greater impact of content-specific coaching in reading and mathematics, and the importance of coaching quality over quantity. The brief offers evidence-based design principles that leader preparation faculty can incorporate into coursework and that school and district leaders can use to develop coaching programs as part of a broader system of instructional support.