Parents have lashed out at a prestigious Australian boarding school once attended by King Charles after teachers punished some students by forcing them to live alone in tents.  

Eleven Geelong Grammar School students at its Timbertop campus snuck out to a local pub earlier this month, where they smoked cigarettes, vaped and tried to call their parents, reported The Australian.

The school launched an investigation eight days later and found that the Year Nine girls, aged between 14 and 15, walked 7.5km to the pub and arrived at about midnight. 

It also found that the unauthorised trip was planned via letters.

Timbertop, where all students complete Year 9, is off-the-grid and it is the only form of communication allowed at the outpost, located in the Victorian Alps near Mansfield.

The letters were sent between one of the girls, her sister and her sister's boyfriend.

As a result, nine of them were subjected to the 'isolation regime' from 6.30pm for five nights as well as after morning tea, lunch and the final school bell.

Five were hit with both internal and external suspension, while two were sent home.

The Australian was told most of the parents knew about the incident but didn't tell the school except one, despite the school claiming otherwise. 

Following inquiries, school principal Rebecca Cody sent a letter to parents saying the rebellious act 'represented a significant breach of a fundamental Timbertop rule: it is essential that we can trust students to remain in their own units overnight'.

'Violating this trust has serious implications for the wellbeing and safety of our community,' she said.

She also said she would reach out with more information on the punishment for the students. 

After learning of the consequences, parents complained about its severity, causing the school to defend its punishment and call out the parents for not reporting the incident.

'In circumstances where school rules were breached; you inform the school of the breach and you acknowledge that it is for the school to apply necessary disciplinary consequences, not that you seek these be deferred for you to action as you see fit,' Ms Cody said in a further letter sent on June 23. 

She also said that this was a 'most unusual' case due to the 'lack of parental support in reporting the incident, and holding students accountable for a choice that placed themselves and others at great risk'.

One mother didn't accept that explanation, calling it a breach of human rights.  

'We wish to place on formal record our serious concern that the isolation regime imposed on (student) during her internal suspension goes beyond appropriate disciplinary practice and into territory that carries documented and well established psychological risk for adolescents,' a parent said. 

'The United Nations Convention on the Rights of the Child, to which Australia is signatory, explicitly prohibits under Article 37 the cruel, inhuman or degrading treatment of children.'

She also claimed she wasn't told what the disciplinary action was, saying the school needed to 'communicate clearly and promptly what a child in its care is experiencing during a period of disciplinary consequence'.

'We ask the school clearly and directly: at what point were you planning to inform us of the full conditions of what our daughter was enduring each day?' she said. 

Many people sided with the school, suggesting the parents were too soft on their children.  

'I am tired of parents not taking responsibility and backing schools,' one said.

'Boo hoo to the parents, they should grow up. Their kids broke the rules and were punished accordingly, so if they don't like it, take their kids out of the school,' a second said. 

'As the saying goes, ''If you do the crime, you do the time''. These parents need to grow up,' a third said.

Daily Mail has contacted Geelong Grammar for comment.