Green’s Dictionary of Slang

floating academy n.

the prison hulks.

1777		Scots Mag. 1 July 8/2: Mignam [...] as well as other defenders, know what they have to depend on if they once enter on board the floating academy.
1781		G. Parker View of Society II 141: The Floating Academy. This is a new insititution.
1782		Oxford Jrnl 7 Sept. 1/2: The above Gang have lately been discharged from that Sink of iniquity the Floating Academy at Woolwich.
1785, 1788, 1796		Grose Classical Dict. of the Vulgar Tongue n.p.: The floating academy, the lighters on board of which those persons are confined, who by a late regulation are condemned to hard labour, instead of transportation.
1791		Caledonian Mercury 20 Oct. 2/3: Mr Duncan Campbell, the Master of the Floating Academy at Woolwich.
1811		Lex. Balatronicum.
1826		C.M. Westmacott Eng. Spy II 212: You see the floating academy as is kept a purpose for ’em, said he, pointing to the receiving hulk for the convicts.
1830		Egan Finish to the Adventures of Tom and Jerry (1889) 140: Many of them [i.e. convicts] [...] had spent a few years on board of the floating academy.
1844		Lloyd's Wkly Newspaper 7 Jan. 5/3: The prisoners [...] are marched to the quarter-deck of the Hulk [...] then ordered 'forward' under the forecastle of this floating academy.
1848		Flash Dict. in Sinks of London Laid Open.
1864, 1867, 1870		Hotten Sl. Dict.
1882		Sydney Sl. Dict. (2 edn) 4: Floating Academies - The hulks.
1895		Crowe Aus. Sl. Dict. [as 1882].