The Whitehouse Centre pupil referral unit is barely visible behind heavy metal gates in a residential street on the Hartcliffe housing estate in south Bristol.

As deputy head Alison Salway opens the gates, the contrast between the building and the neat modern houses that surround it becomes apparent.

"This place was supposed to have been rebuilt years ago," she says, leading the way through the scuffed and scraped main door into the dimly lit entrance lobby.

The pupils who come here for their schooling have been excluded from mainstream education in Bristol, often because of behavioural problems.

The three boys who are waiting in the hallway all came to the Whitehouse Centre after difficulties at their previous schools.

Yet despite being in one of Bristol's pupil referral units, a team of seven pupils, which included Harley Brown, 15, Daniel Buxton, 15, and Luke Gregory, 14, managed to beat pupils from other schools to win the Drugs section of the Sharp Shotz animation competition.

The competition – which also has a Guns and Knives section – aims to encourage young people in the Bristol area to examine complex issues through producing their own animated cartoons.

It was established by the Bristol-based Positive Role Models Agency, and is run in collaboration with Aardman Animations, the University of the West of England, the BBC and Peter Gabriel's Real World Studios.

The entry submitted by the team from the Whitehouse Centre – called Team 10, because they are all in Year 10 – tells the story of a man called Simon who has a drink problem, and is bringing up his eight-year-old daughter on his own.

Called Turning Our Lives Around, it tells how the little girl, Kim, gets injured as a result of one of her father's drinking sessions, leading him to look at his life.

However, Simon is not unsympathetically presented as an alcoholic. Instead, the pupils crafted a more detailed background for him, in which he turned to alcohol in order to drown his sorrows after his wife died giving birth to Kim.

As the boys talk about how they and the other members of Team 10 at the Whitehouse Centre came up with their ideas for the animated cartoon, it becomes clear that they have experienced problems in their young lives that do not affect most children.

Daniel, who was previously at Brunel Academy, said: "Some of us have seen problems caused by alcohol in our own lives.

"We worked out that four out of seven of us in the group had a parent or carer who had been drunk around us."

Luke, who was referred to the Whitehouse Centre from Withywood School because of behavioural problems following the sudden death of his father, added: "Only two out of our group had never been drunk.

"One of the reasons we wanted to do a project on drink was because we thought more people would be able to relate to it."

Harley, who was also sent to the Whitehouse Centre from Withywood School, said: "The father has done a bad thing, but he's not a bad person.

"In the final scene he is shown deciding whether to pick up the little girl's teddy, or pick up his bottle of drink."

According to Mrs Salway, the fact that the team were able to produce a thoughtful script that won the prize shows how far the pupils have progressed since joining the Whitehouse Centre.

"There's always a story behind why pupils end up here," she said.

"But six months ago, most of these pupils couldn't have sat down and told their stories.

"They've faced what has happened to them in the past, and aspects of their own stories and emotions have been projected on to the little girl in the cartoon.

"Doing the project has been a vital part of the process of moving on for them. They've been given experiences of the wider world through working with animation students from the University of the West of England, and going to Peter Gabriel's studios to arrange the soundtrack. You can't put a price on that sort of experience."