The government in Taiwan implemented 12-year compulsory education in 2014. Among its several measures, the newly adopted student assignment mechanism caused intense debate in Taiwan. In this paper, we construct a model in which students submit their school choices and characterize the pure Nash equilibria under both the new and the original system. We then provide an example with a typical mixed equilibrium to illustrate its welfare and efficiency outcome. We find that, under the new system, the best students are not affected while the second-tier students lose and the last-tier students gain. Under the new system, schools will be more likely to admit students from all tiers, although all schools may have vacancies now that only occurred in the least preferred schools under the old system.