CHICAGO (CBS) — Is your child’s backpack too heavy? Often everything a child needs at school can be found in one place-on their back. From books and notebooks to pencils and other school supplies, it all gets toted around in a backpack.

Rush University Medical Center Orthopedic specialist Dr. Joshua Blomgren says all the stuff kids have to bring to school can add up in weight.

“The incidents of low back pain is pretty high. There are some students that reported that it’s as high as 40 percent in 11-14 year old.”

He says the backpack is best worn with both straps over the back and with a wider strap that helps distribute the weight. He also recommends to tighten the straps so the backpack is sitting firmly against the back.

Dr. Blomgren says there’s a good way to tell if your child’s backpack is too heavy.

“One of the easiest way is to look and see as the child is walking, are they leaning forward? Typically this is a sign that they are overloaded.”

Dr. Blomgren recommends these bags not weigh more than about 10 to 15 percent of the student’s body weight.

If that’s not feasible, he says you may want to purchase a rolling backpack.

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