Oh no, that one is definitely true,” stated the headteacher, not smiling and clearly not joking. He could see I was a little confused, so he offered more evidence. “Every time wind whips through that playground, I can guarantee there will be three kids outside my office within an hour. It sounds crazy, but a windy day definitely increases bad behaviour.”

Despite the profession becoming more research-informed, despite the word evidence being thrown about more often than a rounders ball on the playing field, maxims such as this persist in teaching. Even the most rational teacher will tell you “there is probably something in it” when the old wives’ tales of teaching - don’t smile ’til Christmas, teachers always get ill in the holidays - are mentioned.

But are they really true? Does research offer proof of any of these claims?

As a Christmas treat for you, Tes has made it its mission to find out - and to discover whether some other popular claims, such as the ol’ favourite “my dog ate my homework”, are feasible, too.

Are teachers more likely to get ill during the holidays?

You’re on the home straight; end of term is rapidly approaching and you’re already planning how to spend your time off. But then, with just days to go, you start feeling under the weather and get the sniffles. Just as term ends, a full-on cold erupts and you spend the first half of your holiday under the duvet.

Do teachers always get ill in the holidays? There is a distinct lack of research as to whether this is truly the case, and it would be a fiendishly difficult study to do (what constitutes sickness, for example?)

But anecdotally, teachers do report high sickness rates during holidays. There is good reason to believe the claim of higher incidence during this time: “leisure sickness”, a term coined by Ad Vingerhoets, professor of clinical psychology in the department of medical and clinical psychology at Tilburg University.

According to Vingerhoets, there are two possible explanations for this phenomenon. One is that people with very busy jobs are “much more aware of their bodily sensations during leisure time compared with normal working days, because of the distraction by their work”, he says.

“Outside the work environment, it is easier for these internal bodily signals to compete with the strongly reduced external informational input and, consequently, to receive attention. [The] heart of the matter is thus the difference in attentional focus.”

Put simply, you notice you are ill when on holiday, but wade through it when at work.

Another possibility is that physiological processes play a key role in the development of these health problems. “There is evidence that in workers with a high workload, the production of adrenaline is not only increased during working hours, but also during the night and rest periods after finishing work,” explains Vingerhoets. “Stated more simply: the engine keeps running and new energy is constantly produced, while, from a physiological point of view, there is no necessity for doing so. This ‘useless’ energy may result in a disbalance in the body, resulting, among other things, in a weakened immune system, which may imply that one is more vulnerable to [infectious] disease.”

The good news is that teachers can mitigate some of the risk of falling ill before they go on holiday although it does require some personal sacrifices, such as a “sizeable reduction of the intake of caffeine and alcohol”, says Vingerhoets.

Make up your own mind whether that’s a sacrifice worth making.

Does a windy breaktime affect kids’ behaviour?

Windy weather equals wound-up kids - at least, that’s what many teachers believe. But is there a direct correlation between windy weather and wild behaviour?

Rodger Caseby, a former vice-principal at a Catholic school in Oxford who is now education officer at the Oxford University Museum of Natural History, explored whether there was any truth to this widely held belief.

“I’d been reading about evidenced-based practice in education and it struck me that some commonly shared beliefs among teachers - that windy weather makes kids wild being a prime example - weren’t really open to the randomised controlled trials that are the gold standard for research,” recalls Caseby.

He then unearthed a study by Bill Badger and Eric O’Hare, from Lancaster University, who researched the effect that weather had on the behaviour of students at a secondary school in Cumbria in 1989. They found that kids’ behaviour was affected by changes in the prevailing weather conditions rather than the type of weather itself.

His interest piqued, Caseby decided to run his own modest research project when Storm Doris struck in early 2017. To establish if high winds had any bearing on children, he collected data on wind speeds from a local weather station and compared it with behavioural incidents logged at his school over a two-week period, including during the peak of Storm Doris.

His study found no connection between high winds and bad behaviour. Indeed, the school issued 12 per cent more achievement points in the week of the storm than when wind speeds were low.

Caseby admits that “such a small comparison is hardly rigorous research”, but there was “little evidence that windy weather leads to poor behaviour”.

A thesis by Carrie Dabb at Utah State University, meanwhile, reviewed the evidence on the effect of weather on behaviour and found that high temperatures are generally associated with higher crime rates (though this is purely correlation), but little research had looked at the effect of weather on children. Her own small study found “girls and boys were observed to be more active, restless, and/or inattentive” during weather most would perceive as “good”. She notes, though, that there are so many variables involved in behaviour that isolating weather, let alone wind, as a factor would be incredibly difficult (bit.ly/WeatherBehaviour).

What do we conclude, then? There is not enough research to say; research on this issue would be tricky, but it seems unlikely that wind alone could push behaviour to worsen.

And does a full moon make it even worse?

Children sometimes act like little monsters and there doesn’t seem to be an obvious explanation for their radical change in behaviour.

Teachers searching for an explanation will place the blame on all kinds of things - a lack of sleep, too many sugary sweets and/or E numbers, and even the presence of a full moon.

However, most studies that have investigated the relationship between a full moon and abnormal behaviour have failed to find any significant correlation, according to Eric Chudler, executive director of the Centre for Neurotechnology at the University of Washington in Seattle.

“One study with children (bit.ly/MoonEffect) found that moon phase had no association with physical activity, sleep quality or time in bed,” says Chudler. “Another study that involved children (bit.ly/KidWerewolves) showed that sleep duration was slightly (1 per cent or five minutes) shorter at the full moon compared with that at the new moon; physical activity and sedentary time showed no change.

“One additional study (bit.ly/LunarMyth) showed that children were less active, slept for between 2.4 and 4.1 minutes longer and had a few other physiological differences around the full moon compared with half moon and new moon.”

Chudler says it is unclear whether the small differences in sleep duration and physical activity had any significant behavioural effects on children, but he hasn’t come across any data that suggests children’s behaviour is negatively affected by a full moon. He adds that most studies of adults also show “there is no association between moon phase and abnormal behaviour”.

Does the wrong classroom temperature harm learning?

Kids are always moaning that classrooms are either too hot in the summer or too cold in the winter. But is it possible that this distraction could have a detrimental effect on their ability to learn?

To get to the heart of the matter, Joshua Goodman, associate professor at Harvard University, along with colleagues Michael Hurwitz, Jisung Park and Jonathan Smith, looked at the effect that temperature has on students (bit.ly/HeatLearning). The findings of the study made for interesting reading.

“We see clear evidence that, as temperatures start to exceed 70°F [21°C], student learning starts to suffer, and the hotter classroom temperatures get, the more learning suffers,” says Goodman. “Teachers already know this and constantly complain that poorly air-conditioned rooms lead to sweaty, lethargic, distracted students.”

In fact, the study concluded that without air conditioning, each 1°F increase in school temperature reduced the amount learned that year by 1 per cent.

On the flipside, the researchers found no evidence to suggest that lower temperatures “hurt learning, because schools tend to have fairly well-functioning heating systems, but fewer schools have high-quality air conditioning so that heat is more of a problem,” he says.

Can you really work ‘all the hours’, and if so, for how long?

“Pulling an all-nighter” may be a phrase oft used by revising teens and those with an essay due, but it is also common for teachers to say they are just not getting enough sleep.

Indeed, for many teachers, sleep deprivation is a common bedfellow. Work-related stress causes them to struggle to get off to sleep at night and their sleep may be disturbed by worries about lesson planning or whether their kids will make the grade. “I’ve not had a decent night’s sleep in ages” is standard conversation in some staffrooms. But how little sleep can a teacher get by on? And how soon would they notice if their sleep had reduced to a dangerous level?

Not getting enough Zs is a major problem, as it manifests in a number of ways that can have a significant effect on a teacher’s ability to do their job, according to Vicki Culpin, professor of organisational behaviour at Ashridge Executive Education, part of Hult International Business School. “Fundamentally, most of the higher-level cognitive processes we use, such as memory, attention, problem solving, creativity, innovation, decision making, are very vulnerable to sleep disruption or reduction - so much so that often it only takes one or two nights of poor sleep before performance on tasks that require these skills are shown to suffer,” she says.

“In addition, our communication skills and ability to regulate emotions also suffer very quickly after poor sleep.”

Culpin explains that studies have shown that sleep-deprived individuals, given new material to learn, suffer from a 40 per cent reduction in their ability to form new memories.

The physical health of sleep-deprived individuals is also a major concern. “Research has found that individuals sleeping for fewer than seven hours per night for two weeks prior to being exposed to the cold virus were three times more likely to develop the cold than those sleeping eight or more hours per night,” says Culpin. “In the long-term, the effects of chronic poor sleep become very serious, with chronic sleep reduction being linked to seven of the 15 leading causes of death in the US: cardiovascular disease, malignant neoplasm, cerebrovascular disease, accidents, diabetes, septicaemia and hypertension.”

So next time a teacher tells you they have “not had a decent night’s sleep in ages”, don’t just pass it off as hyperbole - ensure they know the risks and see if there is anything you could do to help.

Can you get through in a single day all the chocolate you have been given by pupils?

Around Christmas time, a teacher’s desk drawer often resembles a well-stocked tuck shop thanks to children gifting all manner of sugary treats. And it’s tricky for teachers to resist the temptation to regularly dip into these Xmas goodies.

“I’ll probably get through these by the end of the day,” you’ll hear many a teacher say at Christmas. But eating too much chocolate can lead to tooth decay and weight gain. So how much is too much?

According to the Naked Scientists (bit.ly/OvereatChoc), your body will make you feel sick when enough is enough. This is due to an excess of sugar content from the chocolate leading to hyperglycemia. At that point, you have probably hit the point of too much. And this point will be different for different people.

How much should you eat if you want to avoid your body screaming at you to stop? According to Priya Tew, a nutrition expert for Dietitian UK, adults should only eat four small squares of chocolate - about 25g, which equates to 100-150kcals - per day. She says: “I’d advise people to listen to their own body signals on how to eat in one sitting.”

Wherever possible, teachers should also avoid the milky stuff and opt for dark chocolate, which is high in flavanols and can help to lower blood pressure.

As for the perils of eating out-of-date chocolate - just in case you fail to wade through your stash over the holidays - food experts agree that it doesn’t present a real health danger, as “most of the time sugar is a good preservative”, says Tew.

So yes, some teachers should be able to get through a full pile of chocolate. Whether it is a good idea or not is another matter.

What would happen if a dog actually did eat some homework?

So here we move from teacher myths to pupil myths and a phrase that’s entered into folklore: “The dog ate my homework.”

Slate.com traced the origins of the excuse back to the early 1900s, but it became popularised in the 1970s when it was used in reference to the Watergate scandal and US president Richard Nixon, with psychologist Eugene Kennedy claiming the president was “working on the greatest American excuse since the dog ate my homework”.

Anyone who has ever owned a puppy knows that they will gnaw at anything - homework included - so the concept is sound. But what would happen to a dog if it did take a fancy to a textbook? And if you wanted to further test the claim, would you be met with a hefty vet’s bill?

Thankfully, the ingestion of paper is essentially harmless to a dog, and Daniella Dos Santos, junior vice-president of the British Veterinary Association and a small-animal vet, says it is “unlikely that paper would ever be consumed in sufficient quantities” to cause an animal a problem.

“However, things such as USB sticks in a small dog could cause a gastrointestinal obstruction and staples may also cause issues such as gastrointestinal irritation,” cautions Dos Santos. Which is the most bizarre case against edtech I think has yet been made.

Is it possible to resist smiling until Christmas?

An oldie, but a goodie. This list would not be complete without this favourite. It’s popular advice for teachers for instilling discipline in class, but is it really possible not to smile until Christmas? Six hours per day for 12 weeks?

For some teachers committed to the cause, it may well be. Most of the research around smiling looks at the positive effect of doing it, not how you can stop yourself. But there is quite a bit of advice out there from psychologists about how you can train yourself not to smile. Whether that can be maintained and applied in a classroom with some particularly amusing pupils in it is anyone’s guess. However, the theory is that it should be possible.

Yet where the research is clear is that not smiling for long periods is not a good idea. Smiling can help to lower blood pressure, relieve stress, and it may also be beneficial for people who are struggling with anxiety and depression. “Smiling puts us in a state of gratitude,” explains Sondra Barrett, biochemist and author of Secrets of Your Cells. “Also, as a precursor to laughter, it impacts the immune system and lowers stress levels. Even pretending to smile changes our chemistry - meaning smiling [is advisable] even if you are not feeling that way. The brain doesn’t know the difference.”

Meanwhile, there is a lot of evidence from the service industries that smiling has a positive effect on those being smiled at, meaning more satisfied customers. This is partly explained by the theory of “emotional contagion”: that your emotions can directly trigger the same or similar emotions in others.

So yes, you should be able to not smile until Christmas, but it seems likely it wouldn’t do your health any favours…and it might make your class miserable, too.

Simon Creasey is a freelance writer

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