Jonathan Philip Clayton, aged 27, from Stockton-On-Tees, denied the allegations during a trial at Teesside Crown Court.
However, he was convicted by a jury on all 13 charges on Tuesday (February 4) and is due to be sentenced on February 26.
The sexual touching offences were committed between March and May 2019 while Clayton was working as a supply teacher.
The brave victims, whose anonymity is protected by law, were aged between 7 and 11.
Following the verdict, Judge Howard Crowson told Clayton he can expect a prison sentence. He was remanded into custody ahead of sentencing.
Detective Constable Gillian Gowling, the North Yorkshire Police officer who led the investigation, said: “Jonathan Clayton is a very manipulative individual who used his trusted position as a teacher to touch these young and vulnerable girls for his own sexual gratification.
“He displayed an extremely worrying pattern of behaviour where he would take advantage of situations that arose at school to put his hands on the victims. This was usually when the youngsters were upset and he carried out the abuse under the guise of providing comforting. There were also occasions when he supposedly ‘helped’ the victims to put on or adjust items of clothing, including tights, when they clearly did not require such help.”
DC Gowling added: “Due to the young age of the victims involved, it has been a complex and sensitive investigation. I hope that the outcome at court will help these very brave girls and their families to move on from this terrible experience, safe in the knowledge that justice has been served against the man responsible and he will never be allowed to teach children again.”