half-holiday
From Longman Dictionary of Contemporary Englishhalf-holidayˌhalf-ˈholiday noun [countable] British English old-fashionedHOLIDAY an afternoon in which children do not have to go school SYN half dayExamples from the Corpushalf-holiday• Decorations for bravery won by past pupils were announced at morning prayers, and invariably earned the boys a half-holiday.• A half-holiday was granted in celebration: a reminder of the days when Pemberton granted half-holidays to celebrate his birthday.