school nightˈschool night noun [countable] 
1an evening before a day when a child must go to school: 
The children are in bed by 8 o’clock on school nights.2humorous an evening before a day when someone must go to work: I left the pub at 10, since it was a school night.
1an evening before a day when a child must go to school: The children are in bed by 8 o’clock on school nights.2humorous an evening before a day when someone must go to work: I left the pub at 10, since it was a school night.