And when the last bell rings, the guards return the students to Broadmeadows detention centre, where they live behind barbed wire with their families.

The principal of Glenroy College in Melbourne's north said he was prepared to risk jail by speaking out about the plight of three asylum seeker students at his school, who are waiting to be flown back to Nauru.

"It is about time that we showed a bit of compassion for these young people," principal Paul Dingle said.

"We want all young people to learn and be better citizens. These students have expressed their joy at being at school, being able to interact with peers in a relatively free environment and to be learning. It would be a traumatic experience to have that cut off and for them to have to go back to place like Nauru."

The high school students are among 267 asylum seekers who came to Australia for medical treatment with their families, and could be returned to immigration detention in Nauru within days.

It follows a High Court ruling last week that Australia's offshore processing of asylum seekers was lawful.

Mr Dingle is responsible for the students when they attend the multicultural school, and said it was one of the few places where they feel like normal kids.

They wear the school blazer and tie, play basketball at lunch and chat with their friends in the library. Many of their classmates are unaware of their uncertain future, or the fact that they live in detention. "They are very hardworking, young people and really keen to take advantage of what is offered," he said.

Staff are distressed about the students' future, and the prospect that they may not turn up to school one day soon.

There is growing pressure on the Turnbull government to let the group of asylum seekers remain in Australia. A Department of Immigration spokeswoman said that 48 children of school age were subject to return to Nauru.

Premier Daniel Andrews has called on Prime Minister Malcolm Turnbull to let the group settle in Victoria, and said the state would accept full responsibility for their education, health, housing and welfare services.

Every other Australian state premier has echoed his calls.

Churches and refugee advocates are running a high-profile campaign, and it is understood that other principals are also considering speaking out.

Mr Dingle chooses his words carefully. He could run foul of the Border Force Act, which threatens imprisonment for "entrusted persons" who disclose information about detention centres.

He is not able to say how old the students are, their nationalities or go into great detail about their situation.

"I'm concerned by any push back but it is something that needs to be talked about. We need to recognise how well off we are," he said.

Mr Dingle's school has accommodated asylum seekers living in the nearby Broadmeadows detention centre for two years. He initially thought he would have to closely monitor the students to ensure they didn't run away. "But then I discovered they had no desire to escape. They are happy to be in school, and in the playground with their friends."

Australian Education Union Victorian branch president Meredith Peace said the asylum seekers should not be condemned to a "life in limbo" on Nauru.

"Kids who are seeking refuge have often come from countries in conflict where their education has already been disrupted. They are in Victorian schools getting access to high quality education in a stable environment."

Removing the children would be extremely traumatic and disruptive to their education, she said.

Lucy Honan, a spokesperson for Teachers for Refugees, a group which started in Victoria in December, said Australian schools provided asylum seekers with " a deep source of safety".

"It signifies their connection to the community, with their peers," the St Albans Secondary College teacher said.

"The moment you're taking your kid out of education you are ruining a lot of relationships, and denying that child a future."

She said asylum seeker students were pulled out of school photos and no matter how hard they studied in the VCE, were unable to access Australian universities.

The Age revealed last month that school-aged asylum seekers on Nauru were missing out on an education, because classes are taught in the Nauruan language and bullying is rife. There have also been allegations of sexual harassment and abuse.