School breaktimes are shorter than two decades ago, meaning children are missing out on opportunities to make friends, socialise and exercise, research suggests.
A study carried out by the UCL Institute of Education also indicates that children are now are half as likely to meet up with friends in person as in 2006.
Comparing data from 1,133 primary and secondary schools in 2017 with data collected in 2006 and 1995, researchers looked at how school breaks and young people's social lives have changed.
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At key stage 1, children now have 45 minutes less breaktime per week than children of the same age in 1995. And pupils at KS3 and 4 (aged 11 to 16) have 65 minutes less, according to the research.
Lead author Dr Ed Baines, of the UCL Institute of Education, said: "Despite the length of the school day remaining much the same, break times are being squeezed even further, with potential serious implications for children's wellbeing and development.
"Not only are breaktimes an opportunity for children to get physical exercise – an issue of particular concern given the rise in obesity – but they provide valuable time to make friends and to develop important social skills; experiences that are not necessarily learned or taught in formal lessons."
Researchers found there has been an almost "virtual elimination" of afternoon breaks, with only 15 per cent of children in KS2 and just over half (54 per cent) of KS1 pupils having an afternoon break.
In 1995, 13 per cent of secondary schools reported an afternoon break period, yet now only 1 per cent of secondary schools report having one.
Lunch breaks have also reduced, with three in 10 secondary schools reporting lunch breaks of less than 55 minutes in 1995.
The Nuffield Foundation-funded study suggests that figure has now increased to 82 per cent, with a quarter of secondary schools reporting lunch breaks of 35 minutes or less.
Dr Baines added: "Children barely have enough time to queue up and to eat their lunch, let alone have time for other things like socialising, physical exercise, or exploring self-chosen activities."
Three-fifths of the schools that responded to the national postal survey reported withholding breaks from children when they or their classmates had been poorly behaved or needed to complete work.
Co-author Professor Peter Blatchford said: "We believe that schools should carefully consider the time available for breaks and refrain from cutting them further.
"Policymakers should also consider legislating for time for pupils to have adequate breaks. Whereas working adults, including teachers, have a right to breaks, there is no equivalent policy for pupils."
Geoff Barton, general secretary of the Association of School and College Leaders, said school timetables are "bursting at the seams" because of pressure to prepare children for high-stakes tests and exams.
He added: "It is therefore no surprise that school break times are shorter than they were 20 years ago. "This may be regrettable but it is the result of a conscious decision by successive governments to expect more of schools."
A Department for Education spokesperson said: “The government has given all schools the autonomy to make decisions about the structure and duration of their school day. However, we are clear that pupils should be given an appropriate break and we expect school leaders to make sure this happens.
“We recognise the importance of physical activity in schools to improve both physical and mental wellbeing. That is why our Childhood Obesity strategy reflects the Chief Medical Officer’s guidelines that primary age children should get at least 60 minutes of moderate to vigorous physical activity a day.”