Based on the studies on traffic bottleneck of road, interference area, and mixed traffic flow, a cellular automaton model for the roads in front of elementary and middle school gates during students going to school is established. Characteristics of traffic flow are discussed via the simulation experiment. Effects of the traffic flow and the traffic volume are analyzed including the proportion of student driving private cars, the proportion of school buses, and the command giving by traffic policeman on the scene. Results of examples given in this paper show that traffic safety can be ensured, the traffic jams can be suppressed, and the goal of achieving largest traffic flow and decreasing the passing time of vehicles can be realized by decreasing the proportion of student driving private cars, increasing the proportion of school buses, and assisting the traffic policeman to command on the scene.