Almost three-quarters of school leaders in England are concerned about the impact of the six-week summer holiday on their students' learning, according to a poll.
Headteachers, particularly in primary schools, expressed fear that the lengthy summer break could cause children to forget what they have learned, disrupting the transition to the new academic year.
Some 70 per cent said they were counteracting the postholiday learning dip with voluntary summer reading schemes, while 27 per cent said they had moved pupils to next year's class for the last two weeks of term to help prepare them for September. More than one in 10 secondary headteachers (11 per cent) said they had introduced compulsory summer programmes to help students who might otherwise have to be held back a year.
The findings, from a poll of more than 1,000 primary and secondary headteachers carried out by school support service The Key, come at the end of an academic year in which term times and holidays have been heavily debated. Former education secretary Michael Gove, removed from his post in a Cabinet reshuffle this week, suggested that schools cut the summer break to four weeks; from next year, all schools will be given the power to set their own term times.
The idea of shorter, more frequent breaks was also proposed at this year's annual conference of the NAHT headteachers' union, but it was voted down by members.
Although the poll findings suggest significant concerns, schools in England and Wales already have the joint-shortest summer holidays in Europe, along with Germany and Denmark. Countries such as Italy, Turkey and Estonia close for 13 weeks over the summer, similar to US schools, while high-performing Singapore shuts down for seven weeks.
Academic research supports the idea that longer holidays have a negative effect on children's overall learning, with one US study concluding that two-thirds of the reading gap between rich and poor 13-year-olds could be attributed to the summer break.
Results from the new poll show that 77 per cent of primary leaders are worried about summer learning loss, compared with 60 per cent of secondary leaders. Primary headteachers are more likely to implement schemes to alleviate the problem, with 81 per cent running reading programmes, compared with 46 per cent of secondaries. The Summer Reading Challenge, organised by the Reading Agency, signed up 810,000 primary-aged children to read six books last year.
A US study of summer reading loss shows that disadvantaged students who receive free, self-selected books for three years have statistically significant higher scores in reading tests than those who do not.
Sir Andrew Carter, headteacher of South Farnham School in Surrey, who is running a government review of teacher training, said it was important for children to have time at home.
"I have no objection to the flexibility for schools to change the holidays around a bit, but independent schools shut down before the state schools and come back afterwards," he said. "They don't worry about learning loss, because they are focused. I think there is a bit of summer learning loss but a good school recognises that and gets stuck in come September."
Kevin Bullock, headteacher of Fordham CofE Primary School in Cambridgeshire, said: "Ultimately it would be better to have shorter holidays, but because of the complexities I can't see it happening, unless it is a national move."
Sarah Middleton, head of sixth form at St Peter's Catholic School in Bournemouth, said Year 11 students about to embark on their A-levels were given a two-week project to complete over the summer holiday. "Before we did this, it took two weeks for students to get back into learning. We wanted to accelerate the beginning of term," she said.
The most recent figures suggest that only 4 per cent of academies, which already have the power to set their own holidays, have changed them. Plans to introduce different term times across local authority areas, meanwhile, have been defeated by local opposition.
"For some teachers, a shorter holiday helps pupils to make greater progress, so the benefits would outweigh the costs," said Will Millard, senior researcher at The Key. "Equally, some believe a long summer holiday provides other benefits, because children can spend time with friends and family."