Imagine the scenario. You’re a mother who has volunteered to accompany your seven-year-old son’s class on a trip to the Science Museum in west London and are in charge of a group of five boys, including your son. On the journey home, there’s a problem. As you are waiting to board the Tube, the fire alarm sounds and there is an order to evacuate the station.

What do you do? According to new government health and safety guidelines, there’s a risk you’ll snatch up your son and make a dash for the nearest emergency exit, neglecting the four other boys in the process. As a spokesman for the Department for Children, Families and Schools put it: “There is the potential for divided interest in the case of an emergency.” By contrast, a teacher would try to look after the entire group.

Understandably, parents are outraged that they can no longer accompany their own children on school trips. “I loved taking my eldest daughter and her class on a school trip because it gave me a chance to see how the children interact together,” says Tessa Park, a mother of two, who has accompanied class excursions to the London Aquarium in the past.

Now, with parental involvement being scaled back, her volunteering days are in jeopardy. Just as ministers have published a manifesto calling for more “learning outside the classroom”, Park has received a letter dissuading mothers and fathers from accompanying their own children on trips.

“It’s a very odd attitude,” she says. “I’d like to see the evidence to support this claim that schoolchildren are less safe when they are looked after by a parent. Quite frankly, in the event of an accident I would feel safer if my children were in the hands of a mum who knows their names.”

Park, whose children attend Bute House prep school in west London, is not alone in believing the government has taken a wrong turn. Another parent at the same school, who wished to remain anonymous, is even more vociferous. “Statistically, how many pupils have died on school trips because a parent has saved their child first?” she asks. “There is a greater chance of my child dying crossing Hammersmith Broadway. There are quite a few parents who think this is just the nanny state gone mad.”

She added: “Parents have been going on school trips since time immemorial. If you are a responsible parent, you will manage. This isn’t white-water rafting down the Zambezi; it’s a walk to a museum.”

Bute House was one of several prep schools that attended a course on the issue run earlier this year by Roger Smith, a consultant who is a member of the government’s outdoor education advisers panel. So far Smith has briefed about 600 private schools on the updated guidance. He says that while it is not yet statutory, it is already considered “best practice” not to include parents as supervisors on trips involving their children.

“If a trip did go pear-shaped, a school would be asked why it had not complied with this advice,” he says. Indeed, the consequences can be severe.

Fines and even manslaughter charges have been brought in the past against schools, councils and teachers who have failed to protect pupils on trips. In 2002 a teacher was jailed for manslaughter after an accident in Cumbria when a boy of 10 drowned in a river. In 2003 Leeds council was fined £30,000 after admitting to flawed safety measures on a trip during which two teenage schoolgirls drowned.

The turning point, however, was a tragedy more than a decade ago. In 1993 four sixth-formers died on a canoeing trip in Lyme Bay, in the West Country, in one of Britain’s worst canoeing disasters. Peter Kite, the director of the outdoor centre responsible for the trip, was convicted of manslaughter and jailed for three years.

After this, one teaching union, the NASUWT, told members to be wary of supervising trips for fear of being sued, and nationally the number of excursions fell drastically.

The union has now changed its stance, but insists that children be accompanied by teachers rather than parents. Longstanding guidelines suggest that one adult should be in charge of six seven-to-nine-year-olds on an outing; the ratio is one adult to three for children aged under five.

Chris Keates, general secretary of the union, explains. “We have long had serious reservations about school trips. More and more schools were counting parents in the ratio of adults to children required for a trip, when they should really only be including trained staff.

“While parents can be helpful, it can be hard for staff to get them to understand the safety aspects. Schools are taking a risk if they don’t use qualified staff.” Even on a trip to Kew gardens? To a museum? “On any outing,” she says. Keates acknowledges that “some people might say that not counting parents as part of the adult-pupil ratio will jeopardise trips going ahead but we say that if you can’t get enough qualified staff to accompany them, you shouldn’t be going in the first place”.

Several head teachers spoke out against the guidance last week. Dilys Hoffman, head of Beckford primary school, in north London, said: “I don’t think it’s okay for the government to be interfering with schools’ practice. Sometimes it’s quite a good thing for a parent to accompany their own child, especially if the child has special needs or behavioural issues. Children love having them there.

“Provided parents are given guidance and have had police checks, I don’t think it’s a problem.”

Karen Coulthard, head of Berger primary school, in east London, agrees. “Today our nursery children are going to a pantomime and the ratio is 1:1, so we ask for one parent to accompany their child,” she said. “It’s very important to get the youngest children out and accessing the wealth of resources on our doorstep”. For decades parents have helped schools to do just that.

Additional reporting: Victoria Hollingsworth and Elen Griffiths

Times recommends

• ‘Obama effect’ pushes British pupils to US
• Over-subscribed colleges face budget shortfall
• End in sight for school tables based on test results