A disciplinary appeals committee set up by governers at Cwmdare Primary School in Aberdare, 22 miles east of Swansea in the Cynon Valley, this week decided to let Paul Davies return in September.
It follows a two-year battle to keep his job that ended in a successful High Court appeal last month.
Mr Davies hit three cars in the crash in March 2006, which seriously injured another driver, Kelvin Palmer. The victim's wife, Anne Palmer, head of business studies at Treorchy Comprehensive, said she was appalled that a convicted criminal was about to be allowed to resume teaching.
Mr Davies was banned from teaching in February by a professional conduct committee of the General Teaching for Wales, and prevented for applying for reinstatement for at least two years.
But the High Court set aside the ban, paving the way for Mr Davies to return to his post if the disciplinary committee agreed.
Mr Davies served only three and a half of the original 15-month sentence, although he decided not to return to visit the school for another three months, as he was wearing an electronic tag.
He told The TES: "I was asked by an older pupil, 'Sir, what's prison like'? My answer was: 'It's not a nice place, not somewhere you want to go'."
Mr Davies praised his "exceptional" governors, who he said had backed him throughout.
"I've every indication that the staff are 100 per cent behind me," he said. "In my darkest days, there was always the doubt: are the school's needs going to be greater than their professional commitment to me as a head?"
He said his experience of prison had given him a better understanding of punishment and forgiveness: "If a child does something wrong and you continue to remind them that they've messed up, that child will not attempt anything.
"I've got to bring back something extra to the job. I think my experience will bring things into the curriculum, in a reflective way."