Some parents "visited schools to look for teachers"

Delegates will discuss how best to deal with the problem at the NASUWT's annual conference.

Union president Lorraine Stronge said although it may not happen in every school, it was a serious issue.

"By-and-large, the vast majority of parents are very supportive of teachers in their working environment."

She added: "But on occasion, throughout Northern Ireland - in some schools - there have been instances where teachers have been actually bullied by parents.

"This has been either threateningly down the phone or by visitations of the parents to the school actually looking for the teacher."