Andrew Milewski looked at an "inappropriate" site while teaching a class of 11-year-olds and the "unacceptable images" were seen by the children.
The teacher has been struck off the teaching register indefinitely after the General Teaching Council found him guilty of "unacceptable professional conduct".
Mr Milewski, who worked at Wetherby High School, West Yorkshire, also searched for porn star's biographies and "other similar sites" on the internet, it was reported in the Times Educational Supplement.
It later emerged that he had previously sent an "offensive and abusive" message to a head teacher of another school after being rejected for a job.
He was also convicted of drink driving and failure to stop and report an accident.
Mr Milewski, 29, who suffers from depression, claimed that his inappropriate use of the internet occurred because he stopped taking his medication.
He told governors that it meant he "wasn't thinking through what the consequences might have been".
But the GTC panel said evidence showed he had been behaving in that way "for some time" while taking his medication.
"We consider that accessing pornography within a school classroom when pupils are present is a fundamental and serious breach of the standards that a teacher should observe and the public are entitled to expect," the panel chair Kathy Thomson said.
"By so doing, Mr Milewski failed to put the wellbeing and development of the children first. He failed to apply appropriate standards of personal conduct and thus undermined public trust and confidence in the profession.
"We note that he was responsible for a class of 11 year-old children, some of whom were able to see some of the images that he had accessed on the class projector.
"We find this is a case of unacceptable professional conduct."
The incidents occurred between September 2008 and July 2009. He left the school in July 2009.
He was struck off the Teaching Register indefinitely and cannot teach in maintained schools or non-maintained special schools.
Ms Thomson said his other convictions showed a "lack of integrity" and did "impact in a material way on his fitness to be a registered teacher.
"This case concerns conduct which continued over a significant period of time," she said.
"Mr Milewski spent periods of time where he was clearly not supervising his class adequately."