A jury at Bradford Crown Court took just 30 minutes to bring its verdict on a charge of assault against 47-year-old Ian Blakeley.
He had been accused of losing his temper and slapping a boy who was disrupting a lesson at Crosland Moor Junior School in Huddersfield, West Yorkshire, in December last year.
Outside court Mr Blakeley said: "I don't believe in hitting children, I never have done. I think it demeans the teacher, you lose dignity and in the end you lose authority."
Mr Blakeley went on: "I'm very grateful for the support I have received from the Kirklees community of schools who have been ringing me up and sending me cards non-stop.
"I'm just glad that today, at long last after 11 months, commonsense has prevailed."
Mr Blakeley resigned his post as head teacher at the school in June this year and now works as an education adviser with the local education authority.
His wife, Hazel, 47, a science teacher at a local secondary school, described the proceedings as a "waste of money". She said she was now fearful of walking back into a classroom next week.
Judge Ian Dobkin ordered Mr Blakeley's legal costs for the three-day trial to be met out of public funds.
The prosecution started last December after the 10-year-old boy's father called police alleging his son had been assaulted by Mr Blakeley. The boy, who cannot be named, had told the court the head teacher grabbed him by the throat and slapped him across the face leaving a red mark.
But Mr Blakeley, who lives in Huddersfield and who has been a teacher for 26 years, insisted throughout he had not hit the boy.Reuse content