- school day - any day on which school is in session; "go to bed early because tomorrow is a school day"
--1 is a kind of day
- school, schooltime, school day - the period of instruction in a school; the time period when schools is in session; "stay after school"; "he didn't miss a single day of school"; "when the school day was done we would walk home together"
--2 is a kind of time period, period of time, period
--2 has parts: study hall - school, schooltime, school day - the period of instruction in a school; the time period when schools is in session; "stay after school"; "he didn't miss a single day of school"; "when the school day was done we would walk home together"