Dozens of New South Wales teachers have been investigated for alleged assaults against students with autism, including children being sat on and placed in headlocks, Education Department data shows.

The ABC has obtained figures of alleged child protection incidents involving students with autism spectrum disorder at NSW public schools.

Of the 37 alleged incidents, management action was taken in eight cases, after the conduct was shown to have occurred.

There were several other matters where the incident was proven but action was considered reasonable.

But that was not the case in December last year when a female assistant principal allegedly grabbed a Year 2 student by the neck and put him in a headlock before dragging him along a corridor with his feet off the ground.

Management action was taken in that case, along with another incident where three male teachers locked a boy in a bus and used excessive force while sitting on his knees.

In another incident where action was taken, a teacher grabbed a handful of a Year 5 student's hair to remove the child from a swing.

Another child was allegedly forced to drink soapy water.

No school has been identified.