Though it's tempting to snag a pack that's on sale or that features the cartoon character du jour, keep these practical considerations in mind while shopping for this essential back-to-school gear.

Boy wearing backpack
Credit: Frances Janisch

A backpack leaves with your child in the morning and stays with him until he gets home. It's essential for holding supplies, books, and lunch (and maybe even a few hopes and dreams). So it's no surprise that kids prefer picking backpacks that show off their personality and interests. "The pack is a reflection of the child," says Pam Jones, senior designer of the travel division at L.L. Bean. "If it fails for any reason or breaks, it's more than an inconvenience -- it's like a flat tire." Even if your child gravitates toward a backpack with his favorite character or color, it's important to give it a test run to inspect the quality and see how much the backpack comfortably holds. Do the zippers work effortlessly? Do the buckles easily snap open and shut? Do they feel secure? Flip the pack inside out and look for a "finished" seam; threads should not have frayed edges or fuzz, Jones says. If you're looking to buy a new backpack, keep these key tips in mind to choose one that your child loves and that can also last for a few years.

Shoulder the Straps

Look for a pair of wide, padded shoulder straps to help distribute weight evenly and reduce the risk of muscle strain or injury, says Benjamin Hoffman, M.D., a pediatrician and director of the Tom Sargent Safety Center at Doernbecher Children's Hospital, in Portland, Oregon. Narrow straps and one-strap messenger bags put too much pressure on a small area of the body, he adds. (If worn, messenger bags should be slung across the chest diagonally for added support; don't hang them on one shoulder as you would a purse.) Some packs also come with a waist or chest strap, which provides extra support. When adjusting the straps for your child, make sure that the pack fits snugly around the body and that it doesn't tilt down.

Pinch the Padding

The back panel and shoulder straps should be padded with foam, Jones says. Check for comfort, support, and durability by doing a "rebound test." Give the area a simple squeeze and wait for the foam to rebound to its original shape. "It should not pop like bubble wrap or crinkle like wax paper," Jones says.

Make Room for Essentials

It's important that the backpack can easily fit a 2- or 3-inch, three-ring binder and other classroom essentials. Bigger is not always better, however. "If the foam pad comes to the back of the neck or head, the pack is too large; the foam pack should be relative to the torso of child," Jones says. And be on the lookout for zippered pockets that can securely hold items such as pencils, ID cards, or phones while still offering easy access. Padded compartments for computers and other heavy objects also help ease the load, Dr. Hoffman says.

Consider Materials and Extras

Fabric: Synthetic fabrics, such as nylon or polyester, are more water-resistant but less eco-friendly than natural fibers are, says Rebecca Schuiling, an instructor of apparel and textile design at Michigan State University. If environmental sustainability matters to you -- and your little one isn't too prone to spilling -- look for a backpack made with natural fibers like hemp.

Zippers: Quality zippers that zip smoothly and don't catch on fabric tend to last longer. Typically, Velcro is not as durable as a well-made zipper.

Reflector: For added protection against cars and bicycles in the evening and at night, many backpacks come with reflective paneling. If you have your sights set on a pack that doesn't come with a reflector, add a clip-on one.

Opt for Wheels

A rolling bag may be a good option to lighten the load because wheels mean that kids won't be carrying all the weight of books on their shoulders. However, the convenience of rolling bags comes with two caveats: Your little one must be strong enough to tote the bag up a flight of stairs (if there are no ramps or elevators at the school) and be able to roll it through snowy conditions (if you live in a region that gets snow). So choose one that rolls smoothly and is not too big or bulky for your child, Dr. Hoffman recommends. Or consider ones with two in-line skate wheels. "They are quiet, absorb shock, and wear well, and they're easy to control and less bulky than four-wheel luggage," Jones says. And always look for a sturdy, easy-to-extend handle.

Tips on Packing the Backpack

Don't overload it. A good rule of thumb is to make sure the maximum weight of the pack, when it's fully loaded, does not exceed 10 to 20 percent of the child's body weight, Dr. Hoffman says. For instance, a 50-pound child should carry no more than 10 pounds on her back.

Pack smarter. Store the heaviest items -- books, binders, and laptop or tablet -- closest to the child's back for the best weight distribution.

Make use of lockers. Encourage your child to unload and load his pack frequently, carrying as few items at a time as possible. If your kid has access to a locker or even a tote tray in the desk, she should take advantage of it. Doctors commonly notice more sports-related injuries in children as they grow up, and these may be connected to back strain. "We see lots of lower-back strain with athletics," Dr. Hoffman says. "We don't know if carrying heavy loads plays into it, but I can't imagine that it helps."