Dr. Black says that avoiding problems starts with picking the right kind of backpack. "Padded shoulders are good, particularly straps that are plenty wide. The backpack should be small enough that it doesn't hang down the waist. It should fit on their back, particularly for younger students. If they have a waist strap it's a good thing, helps support weight."
And it's just as important how your students uses the backpack. "Backpacks should be worn with the straps on both shoulders. The backpack shouldn't weigh more than 10 - 15% of the person's body weight. People need to use their locker."