Four staff have been sacked following allegations of mistreatment at a young offenders' unit.
Security firm G4S announced the move after the screening of a BBC Panorama programme which secretly filmed at Medway Secure Training Centre in Rochester, Kent.
It emerged last week that seven members of staff had been suspended.
After the undercover investigation was broadcast on Monday night, G4S said: "Having seen the evidence in the BBC Panorama programme, we can confirm that we are taking the following action.
"Four of the staff suspended on December 30th will have their employment with G4S terminated with immediate effect.
"Three other staff identified in the allegations will remain on suspension pending further investigation
"One additional person has been removed from operational duty pending further investigation."
The firm has requested copies of all evidence collected by Panorama.
Paul Cook, managing director of G4S Children's Services, said: "We are appalled by the behaviour of certain members of staff at Medway Secure Training Centre shown in the programme and I would like to apologise personally to any young people involved in these incidents."
The centre, managed by G4S in co-operation with the Youth Justice Board since it opened in 1998, is a 76-bed facility for young offenders aged from 12 to 18.