Timothy Dingle was sacked from the Royal Grammar School in High Wycombe, Bucks, in April 2006 after a former lover made a series of accusations in a tabloid newspaper, including that he had seduced her online by pretending to be a younger, unmarried doctor.
The General Teaching Council committee in Birmingham found proved an allegation that Mr Dingle "used the school IT systems and equipment inappropriately in the furtherance of personal relationships" after they were presented with 43 separate MSN Messenger chat logs between him and a female internet user with the name "Minxy Mylovely" in evidence.
The panel heard how Mr Dingle used the school's wireless network to chat online to women using MSN - and even invited one to have a video webcam conversation with him live from his headteacher's study in January 2004.
In one conversation, the woman Mr Dingle was talking to asked him: "Does your boss know you talk to strange and captivating girls?"
Mr Dingle reportedly replied: "I am the boss."
The former head also told one woman that there were "too many interrupting cows" entering his office, stopping him sending messages.
Andrew Faux of the GTC said that the records "demonstrate conclusively that he took time away from school to entertain women during the school day".
The former head, who was not present at the hearing, said in a statement: "There were things that were said on the email and MSN that were inappropriate when taken out of context."
Ian Brown, his representative, said that Mr Dingle had been depressed because of the breakdown of his marriage. Mr Dingle said he had no plans to work again in schools. He now acts as a professional mediator.