With all the school supplies children are required to have, for many, lugging around backpacks can feel like lugging around a sack of bowling balls.

Doctors warn that if a backpack is more than 20 percent a child's body weight, spinal disc compression could occur, leading to severe neck and back pain for kids.

"Imagine your disc is like a jelly donut and it's nice and plump, but when you add weight (it compresses)," says Dr. Sheyan Armaghani from the Florida Orthopaedic Institute.

More than 14,000 kids suffer backpack-related injuries every year. If a backpack is over that 20 percent mark, the weight should be redistributed; have kids carry heavier books and lunches in hands.

Also, a backpack should have thick cushy straps and always worn over both shoulders. Sure, the one-shoulder carry looks cool, but could do serious muscular damage.

Droopy backpacks are also a no-no; wear backpacks, especially heavier ones, high on the back and tight.