OrchKids has been offering free, year-round music-based programming to students across Baltimore for 10 years. In school year (SY) 2017-18, its out-of-school-time (OST) program was based in six schools and served over 1,000 children in pre-K through 10th grade. The primary goal of OrchKids is to expose students and their family members to music and provide students opportunities to participate in musical ensembles. This report provides the results of a quasi-experimental analysis of the effects of OrchKids out-of-school-time (OST) program participation on student outcomes. The study included students who participated in OrchKids from 2009-10 through 2016-17. Outcomes examined included mobility out of City schools, student attendance, chronic absence, suspension from school, and performance on state assessments in English/language arts and math. Participants who joined the program in pre-K through 4th grade and persisted in the program for more than one year had higher average daily attendance, lower chronic absence, and were less likely to receive a suspension from school. Participants who joined OrchKids between 5th and 8th grade also had significantly higher attendance, relative to comparison students. Comparisons of participant and comparison students' state assessment outcomes in English/language arts and math also yielded positive findings. [This study was completed through the generous support of the Baltimore Symphony Orchestra.]