两者的意思都是“在上学的晚上”，on school nights 是on school night 的复数形式。

1.on school nights例：On school nights, my mom makes me go to bed at 9: 00.在上学的夜晚，我的妈妈让我9点睡觉。I'm not to go out on school nights, .上学时的晚上也不让我外出。

2. on school night 例：WhyWere you out at a party on a school night 为什么？你昨晚出去参加晚会了吗？We can't be staying out this late on a school night.在学校，我们不准这么晚才回来。

night名词,夜、夜晚如：theaccidenthappenedonFridaynightnights副词,夜间,相当于atnight如：hecan’tgetusedtoworkingnights他不能适应夜间工作.还有一种用法,几夜,也可用nights要就翻译来说,根据语义,大多应选后者night