Green’s Dictionary of Slang

1. a prison, a workhouse; thus boarding-school gloak, a prisoner.

c.1698		B.E. Dict. Canting Crew n.p.: Boarding-school c. Bridewell.
1719		A. Smith Lives of Most Notorious Highway-men, etc. (1926) 203: Boarding School, Bridewell.
1725		New Canting Dict. n.p.: boarding School, in a Canting Sense, is Bridewell, or New-Prison, or any Work-house or House of Correction, for Vagrants, Beggars and Villains of all Denominations.
1737, 1759, 1760, 1776		Bailey Universal Etym. Eng. Dict. [as cit. 1725].
c.1750–1882		B.M. Carew Life and Adventures.
1785, 1788, 1796		Grose Classical Dict. of the Vulgar Tongue n.p.: Boarding school, Bridewell, Newgate, or any other prison, or house of correction.
a.1790		H.T. Potter New Dict. Cant (1795) n.p.: boarding-school gloaks felons in Newgate, New Prison, Clerkenwell Bridewell, &c.
1809		G. Andrewes Dict. Sl. and Cant.
1811		Lex. Balatronicum.
1823		Egan Grose’s Classical Dict. of the Vulgar Tongue.
1835		G. Kent Modern Flash Dict.
1848		Flash Dict. in Sinks of London Laid Open.
c.1850		Duncombe New and Improved Flash Dict.
1859		Matsell Vocabulum 13: boarding-school. Pentitentiary.
1868		J.D. McCabe Secrets of the Great City 359: The Detectives’ Manual gives a glossary of this language, from which we take the following specimens [...] Boarding-school. – The penitentiary.
1882		Dly Dispatch (Richmond, VA) 1 Nov. 3/3: When a criminal has been taking ‘air and exercise’, he has been in the House of Correction; at college, or ‘boarding school’ when in jail.
1890–1904		Farmer & Henley Sl. and Its Analogues.
1895		Crowe Aus. Sl. Dict. 10: Boarding School, the reformatory.

2. a brothel.

1702		T. Brown ‘Letters from Dead to Living’ in Works (1760) II 259: I had a parcel of honest religious girls [...] as ever pious matron had under a tuition in a Hackney boarding-school.
1707		N. Ward London Terraefilius IV 26: A Hackney Boarding-School; where Mechanicks Daughters are Taught to forget their Parentage, and Young Giddy-Brain’d Citizens are so often Cheated with White-Chappel Fortunes.
1780		M.P. Andrews Fire and Water! (1790) 27: She kept the boarding school for young misses at the sign of the Three Chickens.
1797		M. Leeson Memoirs (1995) III 173: The principal of Pitt-street boarding-school.