With the booming of cram schools recently, the effects of cram schooling on academic performance and the opportunity of entering universities are worthy of investigation. Also, whether the cram school participation is stratified by family social economic status needs to be answered. Some studies have touched these research questions. However, no agreements have been reached. In this paper, we first make a careful review of the relevant literature, design adequate variables measurement and statistical technique, and then use "Taiwan Higher Education Data" to re-explore the questions mentioned above. The empirical results show that the effects of all background variables on academic cram school participation are trivial. On the other hand, the effects of academic cram schooling on academic performance and on the opportunity of entering public universities are both significant. Specifically, they both reveal the "ascend first and then descend" pattern. It implies that too much academic cram schooling may worsen students' academic performance and shorten the time students can use to prepare for the inspections and interviews.