When your child walks in the door at the end of the school day, grabbing a snack is likely the first thing he or she does after tossing the backpack on the floor. Schools often schedule lunch early for no apparent reason -- my kid eats at 11:30 and doesn't get out until 3:15. And then there's homework and after-school activities to fire up for, and dinner isn't for a few hours.

That means kids need snacks that will boost their brain power, give them an energy kick, and provide some nutrition. What to serve? Well, the cookies and milk we grew up on aren't the best option ...

Instead, try these six "super foods" that have been shown to improve memory and concentration:

Fruit: Glucose, or blood sugar, is the brain's preferred fuel and promotes alertness. But that doesn't mean cookies and candy are good snack choices. Those simple sugars set the body up for a quick spike followed by an equally fast crash. There's a reason orange slices are the classic soccer game halftime snack -- they deliver a quick hit of slow-to-spike natural sugars along with lots of water. Try sliced-up fruit with a yogurt dip, or an apple and a slice of low-fat cheddar.

Whole-grain foods: Whole grains provide vitamins B6, B12, and folic acid, which one study says improved memory in women who were taking supplements. They also provide soluble fiber, which allows for a slow release of the carbohydrates into your system and a more sustained source of energy. Try a bowl of whole-grain cereal with blueberries (another super food) and skim milk, or popcorn mixed with fruit and nuts for a trail mix.

Avocado: This rich fruit is full of healthy antioxidants as well as healthy monounsaturated fat, which boosts satisfaction. Try whole-grain chips and raw vegetable strips with guacamole, or roll a slice of turkey with avocado and tomatoes.

Nuts and seeds: Also full of healthy fats, as well as vitamins. A handful of pumpkin seeds gives you your daily requirement of zinc, and nuts are chock-full of vitamin E. Try trail mix with nuts, dried fruit, and chocolate chips or a smear of natural peanut butter on whole-grain bread.

Beans: Wrap up refried beans or black beans with guacamole and some chopped tomatoes (all brain boosters) in a whole-grain tortilla, or dip cut-up cucumbers and peppers into hummus (made from a puree of chickpeas; tahini, aka sesame seed paste; garlic; and lemon juice to taste).

Chocolate: Yes indeed, dark chocolate is actually good for you ... IN MODERATION. That translates into treating yourself, or your child, to a handful of almonds and a small square of dark chocolate per day, which is both a healthy and delicious snack. Trail mix with chocolate chips or cocoa-dusted almonds are another healthy way to feed a sweet tooth.

A few other good-for-you snack tips: Try to balance protein, carbohydrates, and fat in each meal and snack, which will help increase satisfaction and decrease hunger. And don't overlook hydration -- kids don't get a lot of opportunities to drink anything during the school day, so make sure they get plenty of water or milk along with their snack.

What's your favorite healthy after-school snack?

Image via mary_thompson/Flickr