This Snapshot highlights key findings from a study that used Bayesian stabilization to improve the reliability (long-term stability) of subgroup proficiency measures that the Pennsylvania Department of Education (PDE) uses to identify schools for Targeted Support and Improvement (TSI) or Additional Targeted Support and Improvement (ATSI). The Every Student Succeeds Act requires states to designate schools with low-performing student subgroups for TSI or ATSI. Identifying the schools that most need support hinges on accountability data that reliably measure school performance. However, random differences between students' true abilities and their test scores--called measurement error--can obscure a school's true performance. [For the full report, see ED626539. For the appendixes, see ED626541.]