England's General Teaching Council cleared Allan Sherwood, who taught at Jonagold school in Gleesons, Cheshire, of unacceptable professional conduct.
It heard he was attacked during his first term after pupils caused pound;5,000 to pound;6,000 damage to windows during a water fight.
He was attacked again in autumn 2003 after he took a kitchen knife away from a pupil scraping putty from the window frame. He said: "I have never been so afraid in my life."
In February 2004 Mr Sherwood was attacked for a third time. The pupil was removed from school but Mr Sherwood decided to leave. Mr Sherwood denied using inappropriate force. He only used force when he was attacked, as a last resort. Charges that he failed to complete risk assessments and that he did not file incident reports were rejected. He was also cleared of failing to maintain the admission register and failing to undertake an investigation into staff members.