I'd say life gets harder, more complicated, and more demanding in the teen years, and this additional level of complexity and stress makes a vulnerable kid regress to earlier coping strategies. My son became combative and hyper-emotional in his teens and my daughter was suspended for the first and only time during middle school. And I found myself with very few friends in high school. (All 3, diagnosed)
The existence of higher levels of sex hormones makes it harder for any individual to understand who he or she is. At the same time, peers are expressing right or wrong ways to be for a boy or girl.
I would say, anything your child can be involved in that has a group element to it - the cast of a play, playing an instrument in band, Academic Decathlon or Math Meet, a sports team, church choir or social group, chess club, anything of that sort - will ensure that there are opportunities for further developing social skills and for having a sense of belonging. So I would encourage trying to get your son into such activities, and then being very supportive - attending games or concerts, scheduling rehearsals, providing rides or equipment, paying for computer camp or band camp, etc.
If your son wants to/can work, that's also an excellent experience in having a sense of achievement, plus some social connectedness.
On the other hand, if school just seems to be too hard on your son, home schooling or online schooling might be necessary. In most school districts, a teen can participate in extracurriculars while schooling at home. I absolutely refused to do home schooling for my teens because I didn't think I could handle that, but now I wonder if I missed a golden opportunity.
Also be alert to signs of co-morbid conditions such as anxiety and depression. Those things can be treated, and can be very destructive to functioning ability if not treated.
Good luck, and keep asking good questions!
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A finger in every pie.