A former teacher already convicted of harassing a former prostitute was banned from teaching this week for making sexual comments to girls in his class.
Brian Ginn, 60, talked in class about using prostitutes and buying drugs and made suggestive remarks to young pupils.
He said to one girl approaching her 16th birthday: "I do not think I can wait that long." He also used foul language in class and said his sixth-form group was lazy and "should be out working".
Mr Ginn was struck from the teachers' register at a hearing by England's General Teaching Council. Imposing the prohibition order, Gloria Hyatt, chair of the committee, said he had endangered the welfare of his pupils by his behaviour.
She said: "His behaviour seriously damaged the pupils in his care and was discriminatory in relation to gender. He jeopardised the welfare of pupils."
Mr Ginn, a design and technology teacher at Duston upper school in Northampton since September 2003, failed to appear at the hearing and made no representations to the panel.
Giving evidence, a former pupil, identified only as F, said: "I felt sick after Mr Ginn made the remarks. I did not expect a teacher to make those comments. He would talk about meeting girls and taking them to his house."
Duston's head of English, Jane McDonald, told the hearing that in a lecture about sexually transmitted diseases, in front of three tutor groups of sixth-form students, he embarrassed the speaking nurse.
"He asked if she knew anyone who could put a condom on with their mouth, because he did," she said. Mr Ginn was dismissed by the school in May 2004 after allegations from a number of pupils.
Those claims were investigated by Paul Hannant, deputy head, who told the hearing that one girl had to take time off from school. "She was deeply affected by the incident," he said.
Former head of Duston Steve Richardson said he had spoken to Mr Ginn about the complaints but the teacher had claimed they were part of a "vendetta"
by pupils he had been forced to discipline.
Mr Richardson said he also claimed that he was raising the condom question as a safety issue, asking if it was safe to put a condom on with the mouth.
Last October, Mr Ginn pleaded guilty to magistrates in Northampton where he lives to harassment of the former prostitute and was given a year's conditional discharge. A spokesman for Northamptonshire county council said Mr Ginn was no longer employed by the authority.