Hi. I have a mild scoliosis. When I was a teenager I had a growth spurt and it got quite painful. Carrying a bag at school, standing for a long time and even sitting at a desk for long periods would cause pain or discomfort. To me, what your son is experiencing is quite normal. I had a short course if physiotherapy and started swimming weekly to build up the muscles in my back.
Nowadays I rarely have problems with my back. Even when I was pregnant. Occasionally, my husband says there's a bit of swelling on my back where the scoliosis is but that's usually after I've worked out. Hopefully your son will stop growing and it'll calm down.
Hope that helps 😊