Can someone at the back please close the blinds?”

It’s a phrase heard across the nation’s schools in those classrooms that are regularly pierced with blinding sunlight. While the teachers in the shadows of north-facing buildings long for the golden glow of natural light, those right in the glare of it often do their best to shut it out.

That’s probably a bad idea. As is placing classrooms beyond the reach of decent levels of daylight. For though the position of a given classroom might not seem important when your September teaching hand is dealt, there is evidence to suggest that having a classroom that receives more natural light might boost pupils’ academic outcomes.

In 2014 Professor Mohamed Boubekri, interim director at the Illinois School of Architecture, conducted a study looking at the impact of daylight exposure on two groups of office workers. One group was studied in a naturally lit office environment, the other in a windowless room. The results were pretty conclusive: the workers exposed to no natural light recorded lower scores when measuring their physical and mental conditions, and slept for an average of 46 minutes less per night compared with their sunlit counterparts.

Last year, supported by the US National Institutes of Health and in conjunction with a colleague from the Department of Educational Psychology at the University of Georgia, Professor Boubekri began a similar study looking at the impact in the classroom. The research examined the behaviour of children in two towns in Illinois; one group in a south-facing classroom that received significant amounts of sunlight, and another in a classroom that faced west and received very little direct sunlight during school hours.

Although the results on the impact on learning are yet to be published, the patterns in sleep tell a similar story to the 2014 study, with children in the south-facing classroom getting an average of 37 minutes more sleep per night. And we all know the evidence linking quality sleep to improved learning (see bit.ly/LearnSleep).

“Light is the most powerful signal that regulates our circadian rhythm,” explains Boubekri, “and the circadian rhythm itself basically regulates our sleep. When our circadian rhythm is off balance our sleep is not regulated.”

OK, so light is important. But we’re not working in caves - can technology not step up when nature leaves us in the dark?

“The amount of light that we normally need is more than the typical electric light levels that we find in buildings,” says Boubekri. “[We need] almost double or triple, and those amounts cannot be provided by electrical lighting systems.”

As well as the amount of light, it is also the quality that is important. Blue light, which has a short wavelength and occurs in abundance in daylight, has the biggest impact on our circadian rhythm. Lamps that attempt to emulate the blue light tend to be very expensive - particularly if you are buying on a school-sized scale.

Also, the colour properties of light can influence our mood in the classroom. Those strip lights that make everything look orange? They are not a good idea.

“The colour rendering index measures how a particular light source shows the true colour of a particular object compared to daylight,” Boubekri explains. “When you have a big shift in colour, that’s when it tends to be very detrimental. It could be psychological, but we just don’t feel very good when we are in a place where we have electric light sources that show a very strange green or a strange red, and we don’t want to be in those environments for a long time.”

Now, all this is very interesting but if you are a school in 1960s building with no capital budget, is this just presenting a problem that you can’t fit?

Thankfully, Boubekri has an evidence-informed suggestion: timing is everything.

“Being exposed to light early in the morning is a lot better than being exposed at midday or later in the day,” he says. “In fact, being exposed to very large amounts of light at the end of the day does more harm than good.

“Arrange outdoor activities, wherever possible, early in the morning rather than late in the afternoon, so that kids can be exposed to a proper amount of natural light early in the day.”

The added extra that comes with more outdoor activities is an increase in vitamin D. An NHS study shows that 16 per cent of UK children have a vitamin D deficiency, which, according to Boubekri, even a window seat won’t solve (bit.ly/NHSvitaminD).

“Glass filters probably 95 per cent of that ultraviolet D wavelength that is needed for photosynthesis that activates vitamin D,” he says. “Contact with sunlight is crucial. I have kids of my own and they just don’t go out as much as we used to.”

In primary, the idea of morning outdoor activities seems more doable, but in secondary such a suggestion may well send the timetabler into a rage. But though it may prove costly in terms of the time taken to rework timetables, it is essentially a free way to boost sunlight for students. As is taking children outside to work where applicable.

And also free, of course, is keeping those blinds open for as long as possible, despite the glare of the sun skipping off exercise books - though weighing up the benefits of daylight against the damage to learning if a child is not able to read their textbook is probably advisable.

Simon Lock is Tes senior digital editor and tweets at @simon_lock_

This article originally appeared in the 7 February 2020 issue under the headline “Why you can’t shove your pupils where the sun don’t shine’