Anne Hovey, the National Association of Head Teachers Cymru's regional organiser, believes the General Teaching Council for Wales's decision was unduly harsh and legally flawed.
"We decided to appeal soon after the hearing," she said. "We've concerns about broader implications."
The ruling by the regulatory body means Mr Davies, head of Cwmdare Primary School in Rhondda Cynon Taff, cannot apply for reinstatement to the teaching register for at least two years. He denied dangerous driving at Merthyr crown court, but was convicted and given a 15-month jail sentence in June 2007.
Last week concerns about the consistency of GTCW rulings were broached at a meeting of the NAHT executive committee.
"In at least one other case it would appear matters directly relevant to the job were given less attention than something which happened outside the school - something that doesn't, in itself, make a person unacceptable to carry on," said Ms Hovey.
Mr Davies lost control of his car in torrential rain on the A465 in May 2006, colliding with three other vehicles. The judge described his driving as like that of a boy racer. One victim, Kelvin Palmer, suffered multiple injuries, is wheelchair-bound and is unable to work.
His wife Anne, a teacher at Treorchy Comprehensive School, said she was disappointed by Mr Davies's decision to appeal.
GTCW disciplinary committee chairman Jacquie Turnbull said the ban was necessary to maintain public confidence in the profession.