Recently there has been an emphasis on how time spent outside of the classroom can affect student outcomes, including high school graduation, with the hope of closing academic achievement gaps along socioeconomic and racial lines. This paper provides experimental evidence regarding a particular type of out-of-school activity--early work experience--on high school academic outcomes for low-income inner-city youth. Using randomized admissions lotteries for students who applied to the Boston Summer Youth Employment Program (SYEP), we estimate the effect of being selected to participate on academic outcomes as measured by administrative school records. We find that SYEP lottery winners are 4.4 percentage points more likely to graduate from high school on time and 2.5 percentage points less likely to drop out of high school during the four years after participating in the program relative to the control group. These improvements appear to be driven by better attendance and course performance in the year after being selected for the program, with the program's impact on attendance persisting into the second year. Survey data suggest that the Boston SYEP may affect academic outcomes by increasing aspirations to attend college, gaining basic work habits, and improving social skills during the summer.