The purpose of this study was to evaluate the impact of Knowledge in Action (KIA) project-based learning (PBL) approach to Advanced Placement (AP) on students' AP examination performance. This study used a randomized controlled trial, with school-level randomization within five large and predominantly urban U.S. school districts, to compare the AP performance of students in treatment versus control schools, during the 2016-17 and 2017-18 school years. KIA students outperformed non-KIA students on AP exams, including within subgroups. The pattern of results was consistent for two years, and within two courses, AP U.S. Government and AP Environmental Science. Though the shift to PBL required considerable pedagogical changes, teachers and students perceived benefits beyond AP performance, and the majority of teachers planned to continue using PBL after the study. Results support teacher-driven adoption of KIA for students from both lower- and higher-income households, and in both courses. [This report was prepared by the University of Southern California's Dornsife Center for Economic and Social Research for Lucas Education Research, the research division of the George Lucas Educational Foundation.]