The new school year is almost here, and the kids are out shopping for backpacks. For them, it's all about style. You need to consider safety.

"They can be very heavy in comparison to how much a child weighs. That can put a lot of strain and stress on them," said Desiree Calamari with Consumer Reports.

She says kids age 9 to 16 are the most likely to get hurt from an overloaded backpack.

You can tell there's a problem when the child has to lean forward to carry the pack. But it's better to get an accurate weight.

"The way our engineers did it -- rather than just weighing the pack, weigh your child first holding the pack and then weigh them without the pack on their back and then subtract the difference," Calamari said.

According to the American Academy of Pediatrics, a loaded backpack should not weigh more than 10 to 20 percent of a child's total weight.

Consumer Reports says a new backpack should have:

Shoulder straps that are contoured and padded to soften the load
A waist belt to stabilize the pack and transfer weight to the hips
Compression straps on the sides to tighten a partially-filled backpack

Remind you kid to always use both shoulder straps.

More information:

Backpacks for Back to School

Good Housekeeping: 5 Best Backpacks for Kids

Five Steps to Safe Backpack Use