Occupational therapist Dr. Paula Kramer says more than half of all backpacks also carry a serious problem.
Dr. Kramer says a loaded pack shouldn't weigh more than 10 to 15 per cent of a child's body weight.
For a 50-pounder, that would be 5 to 7 pounds. For certain teenagers, that would be about 15 pounds.
When the pack is too heavy, kids risk back and shoulder injuries.
And at college, it's an even bigger problem.
85 percent of students at Boston University said they'd had backpack-related pain at some point. Dr. Kramer says the way a backpack sits is also important.
A 2-strap pack should be on both shoulders with the heaviest part just above the small of the back.
For one that comes across the body, Dr. Kramer says, "Weight is on the shoulder. The rest of the weight is on the back and hips."
This may seem like a minor thing, but if a backpack isn't packed or worn properly it can lead to problems in the future.
That's why Dr. Kramer and other occupational therapists are trying to spread the word to parents and to school districts to help prevent those problems.
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