Downing Street is considering forcing schools to open over the summer so they can be used for activities to boost children’s fitness and stop them getting involved in crime.

Theresa May’s advisers have discussed the change with education, physical activity and sports experts who are lobbying for it.

Under the plan, schools in England would start hosting sporting, creative and other activities in their gyms, halls and on sports pitches, but not in classrooms. The drive is intended to help tackle childhood obesity, give under-18s somewhere to go and help tackle the “holiday hell” facing families needing childcare in July and August.

No 10 advisers on health and justice, as well as an aide to the education secretary, Damian Hinds, met the scheme’s backers on Thursday to discuss how it would work.

Dame Tanni Grey-Thompson, the former Paralympic champion, who led the delegation, said school premises could play a vital role if they became “community hubs” over the summer.

“We are ignoring invaluable community assets sitting right on our doorsteps – school facilities – which should be unlocked during the holidays to give every child the opportunity for a healthy, happy summer,” she said.

“Millions of children are being let down and left behind over the summer holidays, forced to choose between days spent in front of a screen or on street corners,” she added.

Other backers include Lawrence Dallaglio, the ex-England rugby captain, the psychologist Prof Rosie Meek, who undertook a review of sport in prisons for the Ministry of Justice, and ukactive, which represents physical fitness providers such as gym chains.

In an article for the Guardian outlining the plans, Grey-Thompson and Dallaglio say: ‘We know the value of schools during term-time. But they have another use beyond that, using a model which puts no additional pressure on staff, resources or budgets; a model which pays dividends both in terms of financial rewards and children returning to school happier, healthier and ready to continue where they left off.”

Speaking after the meeting, one backer said discussions had been positive. They added: “The government are committed to pursuing the idea of opening up schools to provide opportunities for children and their families during school holidays.”

Sport England research shows that 39% of the country’s sports facilities are based at schools. While many are hired out during term-time to generate extra income, they often remain unused during the six-week summer holiday when schools are closed.

It is an avoidable waste of resources that most school sports facilities remain inaccessible over the summer, according to Grey-Thompson and Dallaglio. Children’s fitness levels drop by up to 80% over the summer due to inactivity, research shows.

It is hoped that if ministers give the scheme the green light they would seek to persuade private schools to open up their often impressive sports facilities too on the same basis.

Steve Howell, the headteacher of the City of Birmingham School, England’s largest pupil referral unit, and Adrian Packer, the chief executive of the Core education trust, were among those who visited Downing Street.

Supporters hope that schools, which are struggling financially, will back the scheme as it would not cost them anything or require staff to give up any of their holidays to help out. Sports clubs, arts organisations and other local groups would between them provide the classes held at school.

They want the government to fund the scheme through the forthcoming comprehensive spending review, due this autumn, so that classes can be subsidised to ensure young people from poor families can afford them.

Anne Longfield, the children’s commissioner for England, threw her support behind the switch. She said: “Schools are a rich community resource which all children should be able to benefit from. I support the idea of unlocking those resources so children can use the time outside the school day accessing them to enhance their learning through play, in safe places.

“The potential of play as both educational and fostering social interaction and wellbeing has too often been overlooked. We need imaginative ideas, both resourced and supported to expand the ways children can experience it. I think this is one of them,” Longfield said.

Twenty-four schools in England and Wales made their facilities available to local young people last summer. The pilot showed that the scheme can work and would be popular, backers say.