If kids in class weren't well behaved, the teacher would invoke collective punishment, not allowing anyone in the class to go to the bathroom. And this made Chang feel ill at ease about letting her child study there.
班上同學不乖，老師實行連坐制，罰全部小朋友下課不准去上廁所，讓她覺得不放心把孩子放在那裡。