Using data on student outcomes and school choice lotteries from a low-income urban school district, we examine how school choice can affect student outcomes through increased motivation and personal effort as well as through improved school and peer inputs. First we use unique daily data on individual-level student absences and suspensions to show that lottery winners have significantly lower truancies after they learn about lottery outcomes but before they enroll in their new schools. The effects are largest for male students entering high school, whose truancy rates decline by 21% in the months after winning the lottery. We then examine the impact attending a chosen school has on student test score outcomes. We find substantial test score gains from attending a charter school and some evidence that choosing and attending a high value-added magnet school improves test scores as well. Our results contribute to current evidence that school choice programs can effectively raise test scores of participants. Our findings suggest that this may occur both through an immediate effect on student behavior and through the benefit of attending a higher-performing school.