Always carry a backpack for school correctly. Use both shoulder straps to distribute weight evenly and balance the load. Slinging a backpack over one shoulder strains shoulder and neck muscles. Adjust shoulder straps so that the backpack fits snugly against the child's back and does not hang more than four inches below the waist. A school bag that is too loose or hangs too low pulls the child backward and affects balance. Use the chest or waist strap to help distribute the weight load.
If you find that the backpack's weight is too much for your child, consider using a rolling backpack. It serves the same purpose as a regular bookbag, but a rolling backpack can be pulled along on the ground lessening the strain on a child's back and neck.
Be alert for signs of backpack overload, such as struggling when putting on or taking off the backpack or leaning forward when carrying the backpack. And, practice preventive maintenance. Clean the backpack out weekly and make small repairs before they become big repairs.