Green’s Dictionary of Slang

1. a maximum–security prison; thus gladiator, a violent prisoner.

1934		L. Berg Prison Nurse (1964) 80: The gladiators ignored his sarcasm and allowed themselves to be led away in silence.
1981		Maledicta V:1+2 (Summer + Winter) 266: A gladiator school is a maximum-security prison.

2. a prison with a notably harsh regime and a violent atmosphere; thus gladiator fight, a fight put on to entertain other prisoners.

1971		R.J. Minton Inside Prison 84: By the 1960s the prison had earned the label in the system of ‘Gladiator School’; this was, primarily, because of the never-ending race wars and general personal violence.
1986		J. Ellroy Suicide Hill 11: The judge [...] hit him with five years in the California Youth Authority Facility at Soledad—the ‘Baby Joint’ and ‘Gladiator School.’.
1990		S. Morgan Homeboy 161: Joints all the same, gladiator school.
1992		Bentley & Corbett Prison Sl. 4: Gladiator School [...] This is the name given the prison where the young troublemakers are sent [...] Gladiator schools breed gang members because fighting and criminal activities are the primary lessons learned there. (Archaic: kindergarten).
2000		Other Side of the Wall: Prisoner’s Dict. July 🌐 Gladiator Fight: Fighting set up for the benefit of others.
2001		(con. 1975–6) E. Little Steel Toes 10: Me and Big George are as close to being friends as a white and a black can be in gladiator school.
2003		A.N. LeBlanc Random Family 128: Most of Coxsackie’s inmates were young, so there was lots of fighting. Some inmates called it Gladiator Camp.
2005		Guardian 29 Apr. 14: There was no evidence that Stewart had been placed in a cell with Mubarek as part of an alleged practice known as ‘Gladiator,’ in which two inmates who might attack each other were put together while staff bet on the outcome.
2008		R. Price Lush Life 26: I’ll take another bid in gladiator school over that anytime .
2011		D. Barragan Nuestra Familia 41: Casper and I were chained, handcuffed, and placed in the front cage of the gray goose headed for [...] ‘Gladiator School’.
2020		G. Krauze What They Was 137: HMP Feltham. Gang city and gladiator games. Everyone knows Feltham is greazy.
2023		Rayman & Blau Riker’s 237: [T]hat dorm [...] was extremely violent. They used to call it Vietnam or Gladiator School.