The head teacher of a secondary school screamed abuse at a female student during a meeting with her parents, a tribunal has been told.
Russell Moon, 50, the former head of Phillip Morant School in Colchester, Essex, faces a charge of unacceptable professional conduct, which he denies.
The General Teaching Council heard the head teacher screamed the word liar at student B who burst into tears.
Mr Moon left Philip Morant School in April 2005 after six years in charge.
John Keenan, a former deputy head at Phillip Morant School, told the hearing, sitting in Birmingham, that students staged an informal "sit-in" protest to object to changes Mr Moon had made to reduce noise levels in the school.
Mr Keenan told how student B came face-to-face with Mr Moon, who now works as a consultant head.
Mr Keenan said: "She informed Mr Moon she was going to phone her dad and he replied 'I don't give a toss'.
"Some students expressed dismay at the way the head teacher was speaking."
Mr Moon summoned student B's parents for a meeting, which was a "disaster", according to Mr Keenan.
He said: "Student B was giving her account of the afternoon's events, and made the not unreasonable comment that several staff were sympathetic to the students' concerns.
"Moon screamed the word 'liar' at her and she started to cry.
"Her father stood up and advanced towards Moon, causing me to intervene physically to stop him."
The tribunal has also heard allegations that Mr Moon poured water over another pupil's head to flatten his Mohican hairstyle.
Mr Moon is also alleged to have been rude and aggressive to a parent whose son suffered an electric shock in an accident at the school.
The hearing continues.