Rebecca Harold, 24, of Grecian Street, Maidstone, pleaded not guilty to common assault on a 15-year-old boy at the G4S-run Medway Secure Training Centre.
Twelve people were arrested after a BBC Panorama undercover programme uncovered alleged abuse at the Rochester centre in January.
Nine remain on bail and two have been released without charge.
The government later announced it would take over the running of the facility through the National Offender Management Service.
Ms Harold was released on unconditional bail to face a trial before Medway magistrates on 26 October.
A woman charged with assaulting a boy at a young offenders' centre in Kent has appeared before magistrates.