We assess the potential of academic OST programs through a four-year RCT of an intensive, comprehensive program. The program improves reading comprehension and problem solving scores after two years--but only the latter persists four years later. The program increases matriculation at competitive private high schools and reduces it at academically non-competitive magnet and charter schools. These effects may result from the program's intensity, specific services, and interestingly a decline in academic attitudes. Conversely, we can rule out peer effects, stemming the summer learning loss, or general adult support as mechanisms. (author abstract)