When kids choose backpacks, it’s all about style. But for parents, the key word is “fit.” "The backpack should not be more than 15 to 20 percent of your child's weight," said Kathleen Huddy, textiles director, Good Housekeeping Institute.

The bag’s bottom should not be lower than the child’s waistline. "Sometimes I see kids that are just clearly in backpacks that are too big for them. That tends to be the biggest issue. We see small-sized kids with these gargantuan backpacks, but trying them on makes the biggest difference," said Dr. Jordan Metzl from the Hospital For Special Surgery.

"In order to have a backpack fit properly, you need to tighten the straps so that they are up on the back. Clip the sternum strap, and then make sure that there is a waist strap, and that's also clipped," said Huddy.

And Good Housekeeping says a backpack is too heavy if your child has to lean forward to carry it. "Kids grow relatively quickly between the ages of eight and 16, and so, what fits one year may not fit well the next year, and so you have to keep your mind and your wallet open for that," said Metzl.

Good Housekeeping says a close fitting backpack helps center the weight. So you want to be sure the straps curve comfortable against the body. To learn more, check out the August issue of Good Housekeeping or visit www.goodhousekeeping.com.