They made quite a mound.

I made it seem as if I were looking out at the class and not down at the desk of the boy who had recently moved here as I stood at the podium and counted the pretzels atop it. After that, I did some quick math.

If he ate them all, he’d consume 552 calories. I knew that because after providing my classes with King’s Oat N’ Honey Pretzels during the designated snack time for years, I had the Nutrition Facts committed to memory.

And he did. Before dismissal, the boy consumed 23 mid-sized pretzels — 12 more calories than a Big Mac.

On his way out, classmates joked with him about what they perceived as piggishness. I did not.

What appears to be gluttony could simply be the cloak of poverty. Was this boy getting enough to eat at home? I began to investigate, but a few days later the boy moved again.

His situation saddened me. Changing schools frequently is no laughing matter.

Neither is snacking in school.

Do it properly and eating a snack in school produces a gentle and gradual energy boost that improves brain function and eliminates hunger, both of which increase the likelihood of appropriate classroom behavior. Do it improperly and it produces an immediate and excessive energy boost that still improves brain function and still eliminates hunger — and could even create a sense of euphoria — but these are all temporary.

Too temporary.

About 60 minutes after eating an improper snack, what I call “the crash” occurs, making it harder to concentrate now, easier to overeat later, and increasing the odds of misbehavior until the crash subsides with the passage of time, physical exertion, or the consumption of a second, better snack.

Whether you’re a parent packing the snacks or a student eating them, to keep such crashes from happening, you need to know why they occur. (Since a body is a body and a crash is a crash, parents can apply the explanation provided here to coffee-break snacks.)

A poor snack makes you feel really good immediately because it increases blood glucose rapidly. But that rapid increase causes the pancreas to secrete insulin — too much insulin, really. So instead of the insulin escorting some blood glucose to the muscle cells to provide energy, it escorts so much that you actually have less of it in your blood before the lack of it helped make you hungry.

Having a blood sugar level below your fasting baseline creates “the crash,” which impairs brain function, making it much harder to concentrate and pay attention and much easier for minor classroom disruptions to become major distractions.

But the damage done by a poor school snack does not end there.

Since most school snacking is done to aid brain function and not to replace energy used by the muscle cells, the muscle cells have no real need for what they receive from the insulin. As a result, they reject much, most, or possibly even all of the glucose offered.

This rejection means the glucose gets converted into fatty acids called triglycerides. Insulin again provides an escort, except this time the trip is to the fat stores.

Because of all this, it’s essential for an effective school snack — any snack, really — to increase blood sugar gradually. That mitigates insulin secretion, maintains keeps a relatively stable blood sugar level, aids brain function, and keeps the fat stores from increasing.

Moreover, eating appropriate snacks reduces the odds that you’ll overeat later while eating inappropriate snacks increases the odds of that happening.

So what sorts of snacks won’t spike your blood sugar? Ones that contain the proper balance of the micronutrients.

Something that pretzels, for instance, don’t have — even the relatively healthy ones I offer.

Pretzels, even the healthiest, 100 percent whole wheat versions, are generally 80 percent carbohydrates, and, unless you just worked out for an hour plus and hard, that percentage for a snack is just too high.

But my students are not supposed to eat the offered pretzels in isolation during snack time. They are supposed to supply their own protein source, like low-fat string cheese, a hard-boiled egg, an ounce or so of nuts, or even beef or deer jerky.

Unless you’re eating a snack to immediately replenish the energy you expended from a long or intense bout of exercise, snacks of about 50 percent carbs, 30 percent protein, and 20 percent fat do best to insure optimal brain function between main meals throughout the school day.

Creating a homemade trail mix featuring a 100 percent whole-grain cereal, nuts, and just a bit of dried fruit is one such snack. Two others to consider: low-fat yogurt with an added healthy cereal or low-fat cottage cheese with a bit of fruit.

A bit of fruit can be added to any snack, but don’t forget that drinking fruit juices really isn’t much healthier than slugging down soda.