A charity school at which pupils wear blue coats; specifically. Christ's Hospital, originally situated in Newgate, London, now in Horsham, West Sussex; (later more generally) any charity school; now also in the names of conventional schools, some of which were originally charity schools.
Origin
Early 18th century.
Definition of blue coat school in US English:
blue coat school
noun
A charity school at which pupils wear blue coats; specifically. Christ's Hospital, originally situated in Newgate, London, now in Horsham, West Sussex; (later more generally) any charity school; now also in the names of conventional schools, some of which were originally charity schools.