The Social and Emotional Learning Program Quality Assessment (SEL PQA) is an efficient and effective, research-validated observational tool for assessing adult youth leader practices that support social and emotional learning. Intended to be used for programs serving young people in grades K-12, the instrument builds on the research-validated Youth PQA and over ten years of observational measure development. It also incorporates insights from the SEL Challenge, an initiative dedicated to developing exemplary practices to support social and emotional learning in young people. This report, "SEL PQA: An Overview of Items & Scales," walks through the history of the Weikart Center for Youth Program Quality's SEL PQA development and provides in-depth SEL PQA scale reliability and validity analyses to explore the statistical properties of the SEL PQA in order to demonstrate its success.