Three Ashburton College students have been stood down, after placing a bag over another student's head and claiming to be part of ISIS.

The incident happened last Friday on school grounds, and Principal Grant McMillan says staff acted within minutes of it happening.

"During that bullying incident was some pushing and shoving and the like."

"Students got a manual technology bag and put it over his head, and two or three students started making ISIS comments."

The boys are between 13 and 14 years of age.

He says three ringleaders of the group initiated what happened next.

"They were the ones who threw in the ISIS stuff, and the abusive language as well."

"Those three students have been stood down for five days from college."

McMillan says students are well aware the school won't be tolerating such behaviour.

"It's about informing students but also looking at what the lessons are to learn from this, and the kind of place we want the college to be, rather than sensationalising something and trying to create an anti-culture."

Police have been alerted to the incident.