on school night还是nights on school day还是days

on school night还是nights on school day还是days 是at school days 还是 on school days 还是 in school days on school nights是什么意思 应该是on a school day还是at a school day 是on school day还是in school day on school 还是in school? 为什么On school nights,Nights要复数?the whole night就不用 school days前面应该加in还是on啊, 英语造句：1.tv,school,nights,on,he,can,watch?2.he,his,school,days on school nights是指1——5的晚上?还是7-4? Don’t go out on school nights on school team还是 on the school team