We typically advise limiting your book bag to 10% of your body weight or less. A 150 lb junior in high school, for example, should carry a total of 15 lbs or less.
Schools create rules to keep students from going to lockers for whatever reasons, so many students have to carry prohibitive amounts of dead weight to classes. World history, western civilization, biology, algebra, and English literature get pretty heavy, right?
If a student has more than 10% of body weight to carry, consider something like a small carry-on bag--which is a backpack on wheels.
ANY complaint of back pain in a pre-teen or teenager should be taken seriously. Many of these are exacerbated by carrying school books and supplies, but a significant number of them stem from congenital anomalies in the spine. For example, there are many congenital fusions and malformations of vertebrae in the lower lumbar spine that can affect posture and cause recurrent pain.
If your teenager complains of back pain, look at the shoulders and hips as they stand. Are they the same height from side to side? If not, your child may have a degree of scoliosis. This should be evaluated and corrected as soon as possible.
Here's hoping we all have a great school year. Here's hoping it's an ACTUAL school year with in-person classes, exciting football games, and a prom. Roll Tide.