A General Teaching Council for Wales panel sitting in Cardiff decided that Dr Jonathan Williams, of Neath, was not suitable to become a registered teacher because of his "reprehensible" behaviour.
Dr Williams, 38, was sentenced to 180 hours' community service in 2003 for his part in a violent incident outside the Blaze bar in Aberdare in which two doormen were attacked by a gang of men. One of the doormen suffered a detached retina and fractured cheek.
Detective Constable Sharon Pugh told the hearing that Dr Williams, who was in his probation year at Dwr-y-Felin Comprehensive in Neath at the time, was arrested after being caught on CCTV.
Dr Williams told the panel he only "argued and remonstrated" with a doorman while the incident took place around him. He said: "It was a case of being in the wrong place at the wrong time." He said he pleaded guilty at Merthyr Crown Court because his legal team told him it was the right thing to do.
After a two-week suspension, he returned to Dwr-y-Felin, but said he left six months later because he was embarrassed about his conviction.
After a short spell supply teaching, Dr Williams worked at a university in the north-west of England in the field of cancer research. But he refused to tell the panel where in case it harmed his promotion prospects.
He told the hearing he wanted to return to Wales to teach because he had a young family in Neath and the commute to England was "taking a toll" on him. "I think I can do a good job given the opportunity," he said. "I'm not a threat to children or a violent person."
But committee chair Helene Mansfield said the panel was not satisfied that Dr Williams was suitable to become a registered teacher.
"The committee is concerned at the seriousness of the offence and finds such behaviour reprehensible," she said.
The panel was also concerned that Dr Williams had failed to provide character references, and they had difficulty with his lack of co- operation over providing details about his career since 2003.