Purpose: The purpose of the study was to provide verifiable data regarding the impact Professional Learning Communities (PLCs) have on student achievement in the Juvenile Court School (JCS) system. A second purpose was to measure staff perceptions regarding their support and beliefs about the use of PLCs in the JCS setting. Methodology: This was a qualitative/quantitative study to determine if the implementation of PLCs impacted student achievement on standardized tests such as the California High School Exit Exam (CAHSEE), General Equivalency Diploma (GED), and California Standards Tests (CSTs). The type of research that this study utilized was a mixed-method qualitative-quantitative analysis, which focused on the student achievement of JCS students. The data collection instruments were questionnaires, a survey, and interviews of all JCS school staff in the JCS setting. The quantitative data consisted of standardized test scores on the CSTs, the CAHSEE, Academic Performance Index (API), and GED of students in the JCS setting. Findings: Data analysis revealed that student achievement has increased since the implementation of the PLCs in the SBCSS JCS programs in 2004-2005. Overall, the majority of the JCS staff at all JCS sites believed that the PLCs contributed to the increase in student achievement on standardized tests. Further, the majority of the JCS staff felt that their principals had high expectations for the staff and for the students. A majority of the JCS staff also believed that they were a significant part of the PLCs process, which empowered them to be stakeholders in the decision-making process at their sites. Recommendations: For further research should focus on replicating this study in other JCS programs that utilize PLCs and other JCS programs that do not utilize PLCs. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations maybe obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]