The General Teaching Council for Wales was wrong to discount overwhelming support from staff, governors and parents when it struck off headteacher Paul Davies, 53, after he was jailed last year for dangerous driving, the High Court in London was told this week.
Mr Davies's appeal against his ban is backed by the National Association of Head Teachers. It is believed to be the first GTCW professional conduct committee decision to be challenged in the High Court. It comes as the body faces growing criticism from teachers about its disciplinary processes.
In February, the GTCW argued that Mr Davies had damaged the profession's reputation and showed a "persistent lack of insight into the quality of his driving", which was described by the judge who jailed him as "lunatic".
The court was told by Dinah Rose QC that in March, governors dismissed Mr Davies from his post at Cwmdare Primary School in Aberdare "only because they had no option", after letting him return in January on licence from prison.
"Testimonials from the community, best placed to judge Mr Davies, concluded it had not lost confidence in him," she said.
Paul Dean, for the GTCW, said it was justified in striking him off. "It was perfectly reasonable to decide he had damaged the reputation of the profession," he said.
He added that initially there was no record of apology from Mr Davies, nor evidence of remorse after the accident which left one victim, Kelvin Palmer, confined to a wheelchair.
"When it was discussed, his answers didn't show any awareness of the position of the profession as a whole - they simply talked about his own position," said Mr Dean.
Mr Davies was jailed for 15 months in June 2007 after losing control of his Subaru Impreza on the A465 in May 2006. He aquaplaned across a wet road and hit three other vehicles.
He denied the offence and breaking the speed limit, even though one witness estimated he was doing more than 100mph.
Mr Dean said Mr Davies's conduct was incompatible with that of being a teacher. But Ms Rose said banning him was "disproportionate". She suggested substituting a suspension order until August, when his prison sentence ends and a new academic year begins.
She said he was "an excellent teacher, well liked by parents, governors and staff", and that the GTCW had failed to consider the best interests of the children.
She said governors felt there was educational value in pupils seeing someone who had made a mistake being punished and forgiven. "The emphasis of the school is to teach right from wrong," she said. "As a Christian, he has been the harshest judge of his action."
But Mr Dean said: "The GTCW's concern is much wider than the parents and children of this small school. It is about the reputation of the profession throughout Wales."
High Court judge Mr Justice Blair adjourned his decision until a later date, as TES Cymru went to press. Mr Davies is also due to have a separate appeal into his dismissal heard within the next week.