Julian Ford, 38, was accused of shouting so close to children's faces that they were forced to wipe his spittle away. He was also alleged to have pushed two children against a cupboard, and squeezed the arm of another child until he cried in pain.
The chief witness for the prosecution was Michelle Beaton, a teaching assistant at Hill Mead, the south London primary where Mr Ford worked.
Ms Beaton claimed to have witnessed all four incidents. She told the court that Mr Ford had once taken hold of a child who had done no more than pick up another pen when his own stopped working. On another occasion, he had ignored entreaties that a child spoke no English. Ms Beaton told the Inner London crown court: "He would be very, very close to them, almost nose-to-nose, to the point where he was spitting in their face and they would be wiping it away. That sort of behaviour became everyday."
She also told the court that Mr Ford refused to allow pupils to go to the toilet when they asked.
She said his teaching had initially been good, but his approach to discipline had become unacceptable. "All teachers are fair and firm," she said. "But there was a change in his behaviour and he took it to the extreme."
The jury took half an hour to acquit Mr Ford of one charge of cruelty and three of common assault. Amir Ahmed, his solicitor, said: "The evidence was very poor. I don't think it was in the best interests of justice for this to have proceeded to trial at all. The evidence was from teaching assistants, not from the children themselves. It beggars belief that children would suffer these assaults without saying anything to their parents."
Mr Ahmed claimed that the case should not have reached the courtroom, and blamed internal politics at the school.
Mr Ford qualified as a teacher in 2003. A year later, he was held up as a new-teacher role model by the induction teams of Lambeth local authority.
He was suspended on full pay on June 30 last year.
Ray Sirotkin, Lambeth representative of the National Union of Teachers, said: "He wasn't just someone who struggled. He was obviously an excellent teacher. Suspension has a detrimental effect on all concerned. We need to deal with these cases more quickly, so that employees don't suffer unduly for a serious length of time."
Ms Beaton is still at Hill Mead but Mr Ford remains suspended, pending an internal inquiry by the local authority. A Lambeth spokesman said: "The inquiry will look at all aspects of the case. Serious allegations were made last year, which we were obliged to investigate thoroughly."