Carrying weight from books is good for you. Takes care of your physical fitness and mental fitness.
See https://scoliosisinstitute.com/heavy-backpacks/ for more details.
But children should also be taught how to carry backpacks properly, not unbalanced on one shoulder.
Also, only nerds and dweebs use both shoulder straps.
Rather, I don't think it's a simple matter of education, given that there are also social pressures involved.
Doctors claim that heavy backpacks don't cause scoliosis, but can make the associated back pain worse.