Schools have been warned by police about the dangers of so-called “Facebook parties” after the trashing of a £2million Hampstead house in a notorious post-exams celebration.

Officers made efforts to contact teachers across Camden after the party in June left the homeowner with a £15,000 repair bill.

Some 120 teenagers descended on the rented house in Frognal, including scores of gatecrashers, before officers moved in to shut down the party.

Revellers then clashed with police in Arkwright Road in scenes likened by witnesses to the London Riots – and police are keen to avoid any repeat with the end of term approaching.

Inspector Nikki Babb said: “I raised with schools that pupils’ advertising parties in open on social media can have devastating consequences.

“If people are going to have parties then they need to make sure that they allow people they can trust to be in that house.

“If anybody should not be there, they should be calling police.”

The owner of the Frognal house spent three days cleaning before employing builders to carry out substantial repairs.

The woman, who wished to remain anonymous, complained that she had not been taken seriously by police.

But Insp Babb said there had been no contact – and offered to look into the matter again if a complaint is made.

“We have not had any contact with the family,” she said. “We visited twice on the day, in the early hours and then again later on.

“Unless they report criminal damage, it is not going to be investigated, and we have not heard anything.”

Two youths arrested during the disturbance in Arkwright Road that followed the party on June 6 have been charged this week.

A 16-year-old male will appear at Highbury Corner Youth Magistrates Court on July 31 accused of common assault and using threatening, abusive or insulting words or behaviour that caused another person to believe unlawful violence would be used against them.

A 17-year-old male will appear at the same court accused of using threatening, abusive or insulting words or behaviour or disorderly behaviour within the hearing or sight of a person likely to be caused harassment, alarm or distress.