One of the things about raising a child with social skills challenges is that there are moments when you start to think the child has sort of "caught up"-- and then the peers make a developmental leap that leaves the child in the dust again. It is very frustrating. Recess is also hard because it's unstructured and usually poorly supervised.
School should be helped to understand that DS will need ongoing help with social skills-- both in the short and long term. Someone should be helping now by observing recess and noting what the current difficulties are so that he can be taught appropriate skills. (Being encouraged to ask a teacher for help isn't likely enough-- if he knew when he was about to get himself into trouble, he wouldn't have the problem he has.)
If his friends are all girls, that will be functional until perhaps 3rd grade, but after that he will need boys for friends as most girls will stop associating with boys at that age. It's wise to keep cultivating buddies any way you can, inviting kids over for play dates and so forth as it becomes possible to do so.
It sounds like your DS has made great strides-- so this sounds like it's not a crisis, just another point where the landscape changes and it's time to re-evaluate your teaching strategies. Keep calm and hang in there.
