I've seen it work with math, reading and writing. I also see it working in social skills. Just like learning to read doesn't mean basal readers and worksheets, so, too, learning social skills doesn't mean lots of contact with large groups of one's age-mates. Social skills can be learned in large and small groups, formal and informal settings, among people of all ages, at the park, at the grocery store, in places of business, in places of entertainment, in private homes, with friends, relatives and strangers. Learning to take a proper telephone message is a social skill.
Manners are a social skill.
Communication is a social skill. Taking a chosen item to the checkout stand and paying for it is a social skill. Ordering a meal in a restaurant is a social skill. Writing a thank you letter is a social skill. Comforting a hurt sibling is a social skill.