Longman Dictionary of Contemporary English
Wiktionary
n. (context British English) An institution for the care and education of young offenders; a reformatory
Wikipedia
Approved School is a term formerly used in the United Kingdom for a residential institution to which young people could be sent by a court, usually for committing offences but sometimes because they were deemed to be beyond parental control. It is similar to a reform school in the United States. They were modelled on ordinary boarding schools, from which it was relatively easy to abscond. This set them apart from borstals, a tougher and more enclosed kind of youth prison.
The term came into general use in 1933 when Approved Schools were created out of the earlier " industrial" or " reformatory" schools. Following the Children and Young Persons Act 1969, they were replaced by Community Homes, with responsibility devolved to local councils; in Singapore, which by then was no longer under British rule, Approved Schools continued.
Usage examples of "approved school".
He had come the way of most lab technicians nowadays, with three years of college behind him, the last year in an approved school for medical technologists.