@momofthreeboys -I think we need to separate the general idea of taking summer classes and the idea of previewing classes that will be retaken during the school year. There is lots of room for social growth when kids take summer classes on college campuses. When my son took classes at Vanderbilt there was a lot of social time. The kids also got to see lots of stuff in and around Nashville on the weekends and after hours.
He wished he could do summer lacrosse and take summer classes but it wasn’t possible for him. Interesting classes taken on college campuses are often different from what students study during the regular school year. IMO these are very different and preferable to previewing (insert regular HS class here) and then taking it again in the fall.