Police are searching for two teenagers after a high school in Perth's east was extensively damaged by vandals overnight, forcing the Education Department to advise students to stay home today.

More than 200 windows at Eastern Hills Senior High School in Mount Helena were smashed and several buildings flooded including the drama area, gymnasium and basketball courts.

Police said a number of computers had also been destroyed.

About 40 per cent of the school has been damaged.

Mundaring police officer in charge Jeff Taylor said police wanted to question two male teenagers about the damage.

"We are currently investigating the possibility that two people are involved in the damage caused to the school overnight," he said.

"This is just mindless, senseless vandalism. There's just no need for this type of behaviour."

The gymnasium was flooded using fire hoses. ( Supplied: WA Police )

Glazier Mike Pala said he had so far patched up 224 windows.

"[It's] quite a mess, lot of damage to the gym, computers have been smashed," he said.

Education Department regional executive director Jim Webb said the damage was widespread.

"The English block, the art block, the drama area and even the school gym have all sustained damage," he told 720 ABC Perth.

"It seems the intruders have opened fire hose valves and that's flooded the gym area.

"We are being very careful with the water and electricity. We've got all those areas roped off and secured.

"It's about 40 per cent of the school that is affected."

He said about 50 students turned up to school today and a modified program would be run at the school for them.

Glaziers have repaired 224 windows at the school. ( Supplied: WA Police )

Mr Webb said police would examine CCTV footage at the school to try to identify the culprits.

He said the damage was unusual as the school did not had a history of vandalism.

The school should be back to normal by Monday, Mr Webb said.

Police believe vandals targeted the school between 11:00pm on Thursday and 12:30am on Friday.

They want to hear from anyone who noticed anything suspicious in the area last night.

Forensic police are at the scene.

About 40 per cent of the school has been damaged. ( Supplied: WA Police )

Principal Susanne Vaughan, who has been in the job just two weeks, said the damage was very upsetting.

"The expense to the community and the disruption of education are just tragic," she said.

Ms Vaughan said she was grateful for the many supportive phone calls the school had received from members of the community.

Grandfather Ian Dorrington, who arrived at the school to pick up his two granddaughters, said the damage was shocking.

"It's absolutely terrible because at the end of the day, it's the taxpayer that's got to pick up the bill ... it's disgusting really," he said.

He said his granddaughters were horrified.

"I think they're still in a bit of shock. They're probably happy to have the day off but they're sad too, because they love the school," Mr Dorrington said.