The incident prompted a police operation and a furious reaction from witnesses and pub staff.
But the headteacher at Kennet School in Thatcham, Gemma Piper, has fiercely defended the majority of her pupils who reported their peers’ bad behaviour to her.
Passers-by contacted the Newbury Weekly News to report their shock and horror at the incident, which happened following a school charity fundraising event on Monday evening, December 13.
One witness said: “It was absolutely shocking – around 50 children descended on The Swan pub [in Station Road]. I recognised some of them as Kennet pupils and they were underage, drinking their own alcohol in the pub garden.
“Some were also taking what appeared to be cocaine.
“At one point there were mobs of kids in the street everywhere, shouting and screaming abuse.”
Another stated on social media: “Apart from the drug taking, what I found most shocking was the attitude… I never in my lifetime expected to see anything like this from school kids. It was how I imagine inner London to be, not Thatcham.”
Management at The Swan did not respond to requests for a comment but one staff member said on social media that youngsters had “loads of alcohol and drugs”, adding: “We ID’d everyone that ordered and those being bought drinks, but it soon became apparent things were not as they seemed.
“So we immediately took the stance to remove all of them from site… my staff shouldn’t have to deal with that.”
Headteacher Mrs Piper said she was disappointed in the behaviour of a few of her pupils but said she believed social media reports had been exaggerated.
In addition, many of those involved were not pupils, she said.
And she was particularly upset that a genuine, well-meaning fundraising event had been besmirched by the actions of a few.
She said, in a letter to parents: “The fundraising event was very successful and raised £700 for Sebastian’s Action Trust, a local charity that provides emotional, social and practical care to families of seriously-ill children.
“Our students were very mature in entering the venue, allowing handbag checks and submitting all other bags and coats and coats into the cloakroom before entering the event space.
“Students enjoyed some excellent live music from their peers and it was a lovely celebration for them all.
“The student Rotary Interact group did a fabulous job in organising the fundraiser in conjunction with sixth form leaders.”
However, she went on: “It was brought to our attention that a number of students, and others not at Kennet, displayed antisocial behaviours after the event at a local pub.
“I am pleased that out students communicated this directly this morning as they, too, are appalled at the behaviour of some of their peers.
“At Kennet we pride ourselves on the values we teach and expect our students to uphold at all times, especially when when in our local community.
“We have met with the local policing team today and we are working with them to address the situation directly.
“The poor choices of some have a negative impact on others.”
Appealing directly to parents, Mrs Piper added: “If your child was out in the community, visiting local hospitality venues, please discuss this with them directly and remind them that they are accountable for their own behaviour and that they represent both their family and their school.
“There are many opportunities for sixth form students to take a stand against negative behaviour and show our community the positive power young people have.”
Mrs Piper suggested the fracas which prompted police intervention was prompted by a pupil challenging the antisocial behaviour of others.
A spokesman for Thames Valley Police said: “We were called to Station Road, Thatcham, at around 9.10pm… after reports of a group of youths verbally abusing members of the public and fighting each other.
“A 17-year-old boy from Thatcham was arrested on suspicion of assault and affray.
“He has since been released under investigation.
“Anyone with information should call 101 or make a report online, quoting reference 43210562781.
“Alternatively, call Crimestoppers anonymously on 0800 555 111.”