UPDATE: 5.30pm

A Gwent Police spokeswoman has confirmed that no further action will be taken against the 16-year-old boy.

Four people also received anti social behaviour referrals and had letters sent to parents as well.

Parents have previously voiced their anger that all the pupils were ejected from the prom which cost £35.

Phil Bell, executive director at Chepstow Racecourse, said they were verbally assured that parents would be in attendance.

He said: “In future any proms who want to use our venue will have in the terms and conditions which will be changed to ensure teachers or parents are present and if they are not there at the agreed time the event wouldn’t go ahead. You can’t expect our staff to be put in that sort of risk again.”

He said it is their policy for door staff to check bags and nine hip flasks were confiscated.

A statement from Caldicot School said: “Caldicot School has confirmed that the school does not have any involvement in private functions organised by parents for pupils who come to the end of their Key Stage 4 and their GCSE courses.

"The school holds its Leavers’ Day for Year 11 in June and the behaviour of pupils on that day was excellent and responsible.”

UPDATE: 10.24am

A Gwent Police spokeswoman said a 16-year-old boy was arrested on suspicion of breach of the peace and was taken home by officers. They were called to Chepstow Racecourse at 10.15pm on Wednesday due to "a disturbance outside the venue".

UPDATE: 7.25am

PARENTS say they are outraged after Caldicot pupils were thrown out of their prom at Chepstow Racecourse following alleged unruly behaviour.

The Year 11 prom which was held at the racecourse on Wednesday was due to finish at midnight but 135 pupils were ejected at 10.30pm due to alleged misbehaviour of a group of pupils.

It is alleged that a small group of pupils were trying to smuggle in drink and were being threatening towards staff.

Parents including Leigh Mogg, 36, whose 16-year-old son Tyler attended the prom said she was angry that the racecourse decided to eject all of the pupils and said they did not consider the welfare of the children when they were ejected from the venue early.

She said: “I felt they didn’t care at that point of the safety of the children. Anything could have happened – a lot of the children were walking into the town. Quite a few had booked limousines and had to wait around to see if they could be picked up.”

Parents have also voiced their outrage on the Caldicot Community Facebook page for the prom which cost £35.

Ms Mogg said she spoke with a member of staff at the racecourse the next day who said the children’s behaviour was “disgusting” and “vile”.

She said: “I felt a bit insulted that they were saying those things about our children. When I tried to ask him to elaborate he wasn’t willing to go into that.”

“They shouldn’t tar all the children with the same brush.”

Peter Nurcombe, chairman of governors at the school, said: “Obviously that is something which is not acceptable. This is a private function not a school-organised function.

“As a parent I would have been very unhappy about it. It’s something I certainly wouldn’t want to happen to my children. It is very unfortunate that they couldn’t eject the trouble makers and let everyone else get on with it.”

Phil Bell, executive director of Chepstow Racecourse, said a group of six boys had been misbehaving.

He said: “We were assured that parents would be at the event to ensure the children behaved. There were none.

He added: “It is extremely unfair to blame us. They (parents) need to speak to the organisers of the function – they had a duty of care to their children.”

Mr Bell said they only realised that parents weren’t going to be in attendance at the start of the prom at 7pm. He said they will be reviewing their internal procedures.

Dan Davies, a Caldicot School governor, said he signed a contract on behalf of the prom committee as he felt it was immoral to allow a 16-year-old girl to sign. He said that document did not include that parents were going to be in attendance and said he didn’t sign in his capacity as a governor.