The New South Wales Government has announced a state-wide audit of all prayer groups conducted in public schools following allegations of radical Islam being preached in a Sydney playground.

The NSW Department of Education and NSW Police will issue a memo to all principals today, outlining their obligations to report extremism.

Police will also develop training for the education department on radicalisation and extremism.

Premier Mike Baird said the Government would not allow schools to become breeding grounds for radicalism.

"We need to ensure that everyone is aware of an appropriate process and what to look for and what to listen for," he told reporters in Sydney on Tuesday.

"I don't think any one of us could have imagined four or five years ago the concept of 13- and 14-year-olds being involved in extremism and signing up for terrorist activities. That's something almost beyond comprehension.

"This is an appropriate step to ensure extra rigour, extra care, extra sensitivity to movement, words [and] actions that we may see that might be appropriate to report and take action against."

Sorry, this video has expired Mohammed El-leissy, from the InterAction multifaith youth network, speaks to News Breakfast

Last week police confirmed a year 12 student who attends Epping Boys High School, in Sydney's north-west, was being investigated over allegations he was preaching radical Islam in the schoolyard.

News Corp reported the investigation was looking at possible links between the boy and Milad bin Ahmad-Shah al-Ahmadzai, who was last year convicted of threatening to slit the throat of a Commonwealth official.

Al-Ahmadzai is currently in police custody charged over a number of other violent crimes in Sydney.

Police have not confirmed details of the investigation but said the radicalisation of young people, including school students, was a worsening problem.

'Empty minds able to be swayed' to Islamic State

Mohammed El-leissy from the InterAction multifaith youth network said "quality control" of school prayer groups was important.

"The age of young people now joining [the Islamic State movement] is dropping and we are seeing it go into the 15 to 16-year-old range," Mr El-leissy told ABC News Breakfast.

"It is the empty minds that are able to be swayed into this ideology."

Mr El-leissy said one possible protection would be to enlist professional bodies, which were already delivering religious instruction in schools in some states, to oversee the prayer groups.

"They are proper professional bodies, they are able to give people training so that they are not going in [and] preaching ridiculous things," he said.

"I can't see why you can't merge the two together so the special religious instruction is connected with the prayer groups so the same people are running them.

"They're trained in counselling, they're trained in, obviously, not being radical."

NSW Opposition education spokeswoman Linda Burney said the audit was an important step, but the Government had been slow in its response.

"The police last week made it clear that the issue of Islamic radicalisation in schools is broader than Epping, and it seems to me that the Government has been caught a little bit flat-footed in this instance," she said.