- any night of the week that precedes a day of school
- jocular any night of the week that precedes a day of work
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
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Examples from the Web for school night
It was school-night, but the men were up for fun, so gave the Doctor a holiday.
That evening was school-night again, and Mr. Fabian was interested in hearing if Martha had proved satisfactory.