Chicago Public Schools is working to improve early literacy outcomes through a multiyear professional development initiative for preK-2 teachers. The P-2 Balanced Literacy Initiative aims to improve literacy instruction by training teachers to implement effective early literacy instruction balancing systematic foundational skills instruction with reading and writing instruction involving rich, complex texts. The study compared the reading achievement of students who attended schools that received the enhanced supports (priority schools) with the reading achievement of students who attended similar schools that received only the initiative's standard supports (nonpriority schools). It also examined differences between priority and nonpriority schools in teachers' and administrators' participation in professional development sessions and looked at the successes and challenges of implementation. The study found that one year after implementation of the initiative, attending a priority school did not lead to higher end-of-year reading achievement than attending a nonpriority school after other factors were adjusted for. Teachers and administrators in priority schools were more likely than those in nonpriority schools to participate in the initiative's core professional development sessions. This Study Brief to the full report presents: (1) Why this study?; (2) What was studied and how?; (3) Findings; and (4) Implications. [For the full report, see ED617588. For the Study Snapshot, see ED617589. For the appendixes, see ED617591.]