Emergency services were called to the school on Greer Street, Raymond Terrace, just after 10.30pm on Sunday after reports a demountable was engulfed by flames.

Read more: Raymond Terrace school site to remain closed on Tuesday after fire

Fire and Rescue NSW said more than 25 firefighters battled the blaze for two hours before it was extinguished. The demountable was destroyed.

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"On inspection of other buildings within the school grounds, officers attached to Port Stephens-Hunter Police District observed a number of classrooms had been broken into and vandalised, causing significant damage," NSW Police said in a statement.

Specialist forensic officers examined the crime scene.

Following inquiries, the boys aged 14 and 15 were arrested about 1am on Monday and taken to Raymond Terrace Police Station.

They have both been charged with aggravated break and enter to commit serious indictable offence; destroy/damage property in company by fire, and destroy/damage property in company.

They were refused bail to appear at a children's court later today.

Port Stephens MP Kate Washington said the Thou-Walla Family Centre on the site had been damaged.

It is a School as a Community Centre (SaCC) Project that supports families with children aged up to eight years old and can connect them to housing, health, welfare services and family support services.

Staff wrote on the centre's Facebook page they were thankful "for all your kind words" and their thoughts were with "our amazing Thou-Walla families, past and present".

Irrawang principal Stacy Mathieson told families overnight the school would not operate on Monday.

"I have the unfortunate news that due to circumstances beyond our control, our school will be non-operational," she said.

"Students can access the Department of Education Learning from Home Hub if they wish."

Ms Mathieson said on Facebook that police and firefighters were "absolutely amazing, as were the messages of support from many families".

"There is lots to do, right throughout the school, but we are a strong school community and we will get back on our feet," she said.

Fire and Rescue NSW Acting Superintendent Cameron Wheatley said the incident was a timely reminder that calling Triple Zero for a fire emergency can be the difference between life and death, or a building or other property being saved or destroyed.

POLICE have arrested two teenagers after a Raymond Terrace school fire that destroyed two demountables overnight.

Emergency services were called to Irrawang Public School on Geer Street shortly after 10.30pm after reports of a fire.

Officers from Port Stephens-Hunter police district arrived to find two demountable buildings engulfed in flames.

Fire and Rescue NSW crews attended and extinguished the blaze, but were unable to save the two beings.

"On inspection of other buildings within the school grounds, a number of classrooms had been broken into and vandalised causing significant damage," NSW Police said in a statement.

Irrawang principal Stacy Mathieson informed families that the fire meant the school would not operate on Monday.

"I have the unfortunate news that due to circumstances beyond our control, our school will be non-operational," she said.

"Students can access the Department of Education Learning from Home Hub if they wish."

Port Stephens MP Kate Washington said the Thou-Walla Family Centre on the site was damaged.

It is a School as a Community Centre (SaCC) Project that supports families with children aged up to eight years old and can connect them to housing, health, welfare services and family support services.

Staff at the centre wrote on its Facebook page that they were thankful "for all your kind words" and their thoughts were with "our amazing Thou-Walla families, past and present".

Officers arrested two teenage boys, 14 and 15.

They were taken to Raymond Terrace police station, where they remained on Monday morning.

Inquiries are ongoing.

A crime scene has been established at the school, which will be examined by specialist forensic officers.

Police urge anyone with information to contact Crime Stoppers on 1800 333 000.

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