As your children head back to school, are they lugging too much weight in their backpacks? According to today.com, backpacks should be no more than 10 to 15 percent of your child’s body weight. That means that a 50-pound kid’s backpack should weigh no more than seven and a half pounds. Experts add that it’s not just how heavy a backpack is: The way your child wears it is important too. The top of the backpack shouldn’t be lower than their shoulders, and the bottom shouldn’t hang lower than 2 inches below their waist.