Why do we sleep? This is a question that has baffled scientists for centuries and the answer is that no one is really sure. Some believe that sleep gives the body a chance to recuperate from the day's activities; others refer to it as "beauty sleep" as cells in our skin and elsewhere repair themselves while we snooze. Others think that it is during sleep our brains make sense of the things it has seen and learnt during the day: they believe sleep helps us to learn.
Use an assembly to explain to pupils that a lack of sleep has serious effects on a brain's ability to function. After one night without sleep, concentration becomes more difficult and attention span shortens considerably. Tell your pupils how important sleep is to you and how much you miss it if you don't get enough.
But how much sleep do we need? Most adults need, on average, about 7.75 hours, but the amount we really require is what we need to stop us being sleepy in the daytime.
Even animals require varied amounts of sleep. You could ask pupils which animals they think need the most sleep. The average python sleeps for 18 hours a day, while a giraffe only needs just under two hours.
In humans, the current world record for the longest period without sleep is 11 days, set by Randy Gardner in 1965. Four days into the study, he began hallucinating. This was followed by a period of delusion when he thought he was a famous footballer.
You may want to prepare a presentation showing the most popular sleep positions for humans and how animals sleep.
Chris Idzikowski, director of the Sleep Assessment and Advisory Service, has identified six common sleeping positions, and claims that each is linked to a particular personality type.
The most common is the foetus position. People who curl up to sleep are described as tough on the outside but sensitive at heart. They may be shy when they first meet somebody, but soon relax.
Lying on your side with both arms down by your side is known as the log position. These sleepers are said to be easy going, social people who like being part of the in-crowd and are trusting of strangers.
People who sleep on their side with both arms out in front are described as yearners. They have an open nature, but can be suspicious and cynical. They are slow to make up their minds, but once they have taken a decision, they are unlikely ever to change it.
If you lie on your back with both arms pinned to your sides, in the soldier position, you are generally quiet and reserved. People who sleep like this don't like a fuss, but set themselves and others high standards.
In the freefall position a person lies on their front with their hands around the pillow and head turned to one side. Freefallers are often gregarious and brash people, but can be nervy and thin-skinned, and don't like criticism or extreme situations.
Finally, starfish sleepers lie on their backs with both arms up around the pillow. These people make good friends because they are always ready to listen to others and offer help when needed. They generally do not like to be the centre of attention.
With these facts explored, you could round off the assembly by mentioning that one thing that all experts agree on is that too many teenagers are damaging their health by not getting enough sleep and by falling asleep while wearing electrical gadgets. Experts believe that about a third of 12 to 16-year-olds sleep for only four to seven hours a night, when the recommended time is eight hours.
A large proportion of teenagers admit to falling asleep while watching television, listening to music or with other electrical equipment still running, leading to what experts call poor quality, "junk" which is of neither the length, nor quality that it should be to give the brain the rest it needs.
So, remind your pupils that the next time the person looking after them tries to march them off to bed, they should not complain. After all, they may end up better looking and more intelligent as a result
To download slides to illustrate this assembly, visit www.tes.co.uksleepassembly.