Delaying school until at least 9.45am for senior students is a “no brainer” because of teenagers’ different sleep habits, researchers say.

Around half of New Zealand teens do not get enough sleep or get poor-quality sleep, which is linked with poorer mental health, attendance rates and academic performance.

Yet despite international research showing clear benefits of letting teens sleep longer in the morning, few schools in New Zealand have chosen to change their hours. The first school in New Zealand to push back its start time has now scrapped the policy.

With mental health problems and absenteeism on the rise because of the Covid pandemic, it is now time for schools to reconsider the idea, a group of researchers say in an opinion piece published in the New Zealand Medical Journal today.

“To us, it’s a common sense, no-brainer type of approach that actually benefits all,” said Professor Barbara Galland, leader of the Sleep Research Group at the University of Otago and co-author of the opinion paper.

Her research group wants to find out why there is resistance to different school hours, and is surveying parents, teachers and students on the subject. It is also carrying out its own research on later start times, to build on overseas evidence.

Research on later school start times has been led by the United States, where classes typically start at the relatively early time of 7.30am. Some states have started to push for later hours, including California, which has passed a law requiring no school to start earlier than 8.30am – still too early for older students, Galland said.

Teen sleep patterns changed at puberty to favour later bedtimes, a shift which lasted until around age 21 and meant that they needed later wake times. Waking a teen at 7am was similar to waking an adult at 4am.

The NZMJ article cited research showing around 40 per cent of New Zealand teens slept less than the recommended eight to 10 hours a night, and 60 per cent said their sleep was poor quality. This was influenced by a range of factors, including use of electronic devices, after-school activities and homework.

Lack of sleep did not only affect attendance rates and academic performance, but overall health and wellbeing. Poor sleep and mental health were “inextricably linked”, the opinion piece said.

Adolescents also accumulated sleep debt over a week, and felt they had to catch up by sleeping more during weekends. This led to a condition called “social jet lag” because it was a similar to moving through time zones.

Galland said delaying school start times for Year 12 and 13 students was an “attractive, non-stigmatising” approach which could address these adolescent sleep issues.

Rule changes in 2016 gave boards of trustees more flexibility to choose their own start times, but few schools have taken this step.

Wellington High School was among the first to change its hours in 2006, allowing senior students to start at 10.15am and finish at the same time as other students.

Principal Dominic Killalea told the Herald that it was “an interesting experiment” but the school had now abandoned the policy.

“Over time we found more and more students didn’t want a late start so it became optional,” he said.

“Although the idea was nice in theory, it compromised student subject choice and so we moved to more flexible timetabling.”

Killalea said that the school did not observe an improvement in achievement due to a late start.

“In fact, it could be argued that achievement declined until we put into place more flexible programming.”

It appears part of the problem is that if students want to study six subjects, they will have to finish school later – a change which some teachers are opposed to.

Some New Zealand schools allowed students to start later once a week, usually on a Wednesday. This could actually disrupt sleep patterns further, Galland said, by making students “change time zones” three times a week.

She said there was a range of reasons that more schools had not changed their hours.

Parents with more than one child at school did not like the idea of more than one “drop-off”. Some students would also be left alone at home for longer. It also had implications for transport, such as school bus services.

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