This study documents the collective capacity of the external support providers working to improve K-3 reading outcomes in New York City. Interviews and social network surveys with a sample of the 112 providers at work in this "reading improvement sector" showed that they serve as a conduit for sharing reading-related resources and expertise throughout a large part of New York City. However, the collective impact of the sector remains limited because their goals vary widely; support is unevenly distributed; and many programs work in isolation and are informed by funders and sources of expertise that are unlikely to be connected.