Sean Sennu, who worked at Heathcote school in Chingford, north-east London, faced seven counts of unprofessional conduct when he appeared before the General Teaching Council for England.
The hearing was told he took a month-long trip to Ghana in December 2000 which, coupled with other absences, left pupils without the knowledge essential to pass their tests and GCSEs.
Barry Hersom, Heathcote's headteacher, said: "It is my view that Mr Sennu's conduct did serious damage to the education of his students and disrupted the children's continuity."
Robert Bourns, presenting officer, told the GTC that Mr Sennu had taken unauthorised absence, failed to set work for children while absent and often left them unsupervised when he taught at the school in 20001.
Mr Sennu was also accused of failing to ensure coursework was completed, submitted and marked, to comply with management instructions, and of not producing adequate student records.
Mr Sennu, now working as a supply teacher at Mayville junior in Leytonstone, east London, said he had to leave Heathcote suddenly to visit his wife who had been taken ill in Ghana in November 2000.
He said a deputy head had told him that his lessons would be taken care of.
He informed his head of department and signed a "leave of absence" form.
But when he returned, Mr Sennu claimed Mr Hersom had kept a log of his absences.
In a meeting with the head and a union representative, he alleged Mr Hersom told him: "If you don't leave the school quietly, I will make life difficult for you."
Mr Hersom told the hearing several meetings had been set up with Mr Sennu to discuss his problems and "offer him support", but that he had failed to attend on every occasion.
Mr Sennu said a number of meetings had gone ahead that involved Mr Hersom making threats and asking him to leave the school. When he returned to work he said the attitude of other teachers had changed.
The hearing continues.