Ben Williams, a  teacher at Ysgol-y-Deri in Penarth, denies unacceptable professional conduct over three separate incidents in December 2014.
Two involved pupils with Down's Syndrome and the third a pupil with autism spectrum disorder and behavioural difficulties.
The Education Workforce Council hearing in Cardiff continues.
A fitness to practice committee was told Mr Williams was suspended from the school after the third incident at the school, which had opened two months earlier.
Matthew Richards, representing Mr Williams, said he had been the victim of a "vendetta" by headteacher Chris Britten and governors following earlier disciplinary issues.
A teacher at a special school in Vale of Glamorgan left three of his pupils unsupervised, a hearing has been told.