There is a growing trend of children and teens sending provocative pictures or videos of themselves or others to their friends via mobile phones.

The name sexting comes from the term texting, where people send text messages to each other through their mobile phones.

There were at least three serious incidents of sexting reported in the Hunter and Central Coast last year.

In an information sheet sent home to parents, the NSW Education Department urges them to warn their children about sexual predators and to learn how to use and monitor their children's mobile phones, Facebook and MySpace internet page accounts.

A NSW Education Department spokesman said more young people seem to be distributing highly suggestive or even sexually explicit photos of themselves to their friends "often without a real understanding of the consequences".

"The easy availability can turn what can seem an innocent joke or flirtatious fun into a potentially devastating experience - with young girls most at risk," he said.

"It is illegal to take sexual photos of children and young people and it is also an offence to pass them on."

He said they had given principals strong powers to deal with the behaviour.

"Any student engaging in this behaviour will be punished . . . including suspension in some cases," he said.

Concerned parents can ring an advice line on 1300 1300 52.