Teacher Bob gets to his class at the end of the lunch break and tries to get some order. It's a struggle: the students are raucous and excitable, obviously still engaged in their own interests. The students don't seem to want to focus on the lesson.

Being a dedicated teacher, Bob has snappy visuals and a game ready, but it doesn't work. He decides to give up on the fun presentation and moves the class into a bookwork task - this class takes the book seriously. This works and the class begins to settle, but they are still listless and it's obvious they aren't concentrating.

About 30 minutes into the lesson, things are finally quiet. But now, while he is discussing the answers to the book exercises, the students are getting really snoozy: some students are actually nodding off! Bob gets angry.

Sour classroom management

This story is not mine. At a workshop on classroom management recently, teachers were discussing problems they were having in their classrooms. One teacher announced he was having trouble with students sleeping in class. Other teachers in the group nodded: students doze off in class.

One teacher's interpretation was that students don't want to study. They hate English and are disrespectful. The workshop teachers wanted a handy discipline tool to deal with this.

However, a manager or a teacher trainer looking in on Bob's class may have a different interpretation: the students are bored. Bob's poor planning, his geriatric pacing, and teacher-centered activities are killing enthusiasm. This is a possibility.

A visiting sociologist, on the other hand, may decide the problem is a result of the children staying up till midnight doing homework under parental pressure and test washback, and therefore not getting sufficient sleep. Also possible.

There might be another reason, one which falls outside of the realms of pedagogy but is becoming increasingly pertinent to the modern teacher: food and exercise.

Now it's not the responsibility of language teachers to dictate what or when students eat, nor how much physical activity they do outside of the classroom. But these factors affect our lessons, and so even though we can't control them, it's probably a good idea to understand what's going on.

Sweet treats

Our students eat. That's a good thing, except that after sweet snacks things can get complicated. This is most noticeable (for me, anyway) with kindergarten children who can't inhibit their impulses. The cause?

As an English teacher I don't promise to have all the facts right, but here's how I understand it. Blood sugar level is the amount of glucose in the blood. The body tries to keep blood sugar levels balanced - a state of homeostasis. Blood sugar is regulated through the release of hormones. If your blood sugar is too low, catabolic hormones like glucagon are released to help increase it. If it's too high, insulin is released to reduce it. So when we eat a sugary snack (or a large lump of carbohydrates), blood sugar rises and insulin is released.

Over time, the constant intake of sugar (compounded by a sedentary lifestyle) leads to insulin resistance, which means that ever greater amounts of insulin are released to deal with a rise in blood sugar. Large doses of insulin mean that blood sugar levels are then brought down too far. When this happens, the body responds by shutting down to conserve energy. So after a massive intake of sugar, there is a spike of activity, and then a 'crash' during which the body craves sleep. The science here is fascinating, and if you are interested, check out Jeff and Ritah's very readable book  on the subject.

Bitter aftertaste

For me, sugar crashes happen most often in the hour or so just after lunch. Put me in a quiet room with the hum of a pleasant air-conditioner, and I'm history. I can get insanely sleepy during afternoon classes even though I've had a full night's sleep. I promise, it's not because I'm insolent or disrespectful, nor because my mother kept me up till midnight doing my homework. It's just biology.

In our classrooms, unstable blood sugar creates interesting behavioral traits. When blood sugar is high, students are bouncy, fun and uncontrollable. After the release of insulin, they become lethargic. In both cases, focus and concentration suffer. With our increasingly sugar-rich nutrition, this is becoming a topic teachers really should know about. On the topic of sugary diets, have you seen this visual of the sugar content of various drinks?

I'm not sure where this comes from or how accurate it is, but oh dear! Lemon tea - you traitor!

Sugar high

Is there an easy solution? It seems not. Sugar releases dopamine, which is a neurotransmitter that regulates movement and controls the brain's pleasure centers. When dopamine is released, we feel good. Because of this, sugar is powerfully addictive. In this experiment, rats exposed to both cocaine and sugar preferred sugar when given the choice. Restricting sugar to sugar-addicts (of any age) leads to a dopamine imbalance, and in turn, to symptoms not unlike cold turkey. Oh dear (again)!

Back to Bob. Are his kids disrespectful? Is he suffering from poor classroom management? Maybe. But even if Bob has an amazing lesson planned and executes it with aplomb, his students are in the throes of biological forces beyond their reckoning.

Anger is a poor option. A key part of classroom management is maintaining perspective - by this I mean that a teachers need to know not only what's wrong, but why it's wrong, and then focus attention on the elements of the lesson that are in their power to manipulate - like pacing, activity choice, student grouping, and language scaffolding. Some things are out of a teacher's hands, and these need a little shoulder shrug and maybe a quiet chortle. I would say that the students' blood sugar is one of these.

Does that mean ignoring it? That too is a poor option. Teachers who understand the problem have different approaches to minimizing it - like breaking out an activity with movement, or distributing jelly candies, which have the effect of stabilizing blood sugar. Bananas also help. At worst, you can always eat the candies and bananas yourself.

Steve has been a teacher and teacher trainer for over 30 years, and is currently a lecturer on the Master’s in TESOL program at King Mongkut’s University of Technology Thonburi in Bangkok.