Advice for my 13 year old

Hi everyone, Sorry in advance for a lengthy post, I hope some can take the time to read. I joined this group as I believe my son has social anxiety and anxiety in general. Well, I know he does. He has always been shy and a worrier, but never seemed to have issues making friends or socially overall until this year, the dreaded 7th grade. The first half was ok but the second half he started feeling 'sick' a lot and missing school and his grades dropped (a bit, nothing crazy but noticeable). He came to me one night a couple of months ago in tears, and told me how he'd been feeling and had been feeling for a while. He feels lonely and sad, and like he doesn't know what to say or how to be funny and freezes up, even with friends. Physically shaking when having to speak in front of the class. I have noticed that he doesn't get texted a lot or isn't part of many group chats, and when he is he never really responds to anything and eventually fades out. Btw as a mom I hate that kids have to deal with texts and group chat stuff, things I didn't have to but I know are part of life and social life now. The more he told me and the more I looked into I do think he has social anxiety (he also worries a lot about other things like his health, bad storms, someone breaking into the house). We have started therapy and cbt. He is also one of the youngest boys in his grade and on the smaller side - I think he will eventually catch up but there are boys more than a year older than him because where we live everyone seems to hold their boys back a grade, and we just followed the regular guidelines and started him on time. So, there is so much more background here but I know this post is long - my husband and I are considering having him reclass to 7th grade again. He had a good friend who did this last year and who would be in his grade, and 2 other boys from his grade are doing it (not exactly sure of their reasons). It is a pretty normal thing to happen here, especially for boys. We will keep him in therapy and everything we can to help but we also thought him having another year to work through some of the anxiety, have therapy, and being on the older side instead of younger may help his overall confidence as well. In a lot of ways he is just not as socially or emotionally mature as his classmates and it has become clearer in middle school to me. So I guess my question would be to those who started feeling this in middle school, do you feel an extra year may have helped emotionally/socially/maturity wise? I so want to help him any way I can and to do the right thing. I myself have always been shy and introverted and I don't think there is anything 'wrong' about it, it is just the way some people are. I want to give him the tools to help as I hate to see him sad and feeling 'worried and nervous about everything all of the time'. So I guess my basic question is thoughts on reclassing. I don't in any way expect it to be a miracle 'fix' or anything, just that it may give him room to breathe and a some more confidence, not only for middle school but looking ahead to high school and college as well. Thanks so much for any thoughts, I joined this group in order to help him but as I have anxiety myself (genetic, I know) it has helped me too. Sorry for the long post!