I'm assuming you mean gcses? Lots of people take gcses in college, I did when I was 17 because I was too anxious to do them when I was 16, the way I did it was to go full time, I was with people aging from 16 to 24 and I got a fair few gcses. Another way to do it is at evening classes, or a lot of people go straight to A levels and get gcses at the same time with just a few hours of classes a week (quite a few people in my A level class are doing this).
College is not like school, you wear your own clothes, only have to show up when you have a class, you don't have to call the tutors mr or miss or anything, you just call them by their names. People tend to be a bit more mature in college and you're not treated like kids. From my experience college students are a lot more supportive of each other than school kids. Mainly because some of the students are adults and have an influence on the younger people there.
College is of course stressful for someone with SA, but I quite enjoyed doing my gcses and I'm in a different college studying A levels now, and I'm still enjoying it. Hope this helps a bit x