An evening class for aspiring DJs at a school had to be broken up at 3.30am when it turned into a rave with 250 people.
Rushcliffe School, which regularly lets out its hall for external events including birthdays and meetings, had expected a small group to take part in the Saturday evening class between 7pm and 10pm.
Videos and pictures posted on social media showed young people partying with glow sticks and what appeared to be cans of Red Stripe lager.
The rest of the building was locked for the event and the hall was meant to be closed at the end of the session, organised by Field Sports Management.
Steve Lewis, head teacher at the Nottinghamshire school, told : "Sadly staff were not on site, the person was known to [Field Sports Management]. They were given the responsibility and that responsibility was placed in the wrong hands.
"There were 250 people and it lasted until 3.30am, and at one point the fire brigade got called out because the smoke alarm went off.
"We are absolutely mortified by it. It is nothing that the school would ever want to be connected with, or Field Sports Management. We are part of the community and want to support it and be good residents."
A Nottinghamshire Police spokeswoman told ITV News: "Nottinghamshire Police were called just before 2am on Sunday (12 March 2017) following a report of an alarm being activated at Rushcliffe Comprehensive School.
"Officers are satisfied that no offences have been committed."
Field Sports Management have been contacted by ITV News for comment.