Community gardens, sports, religious or interest groups, collectives, contributing in a large household, early work experience, hobbies/interests. It probably is a fairly finite list because societies have optimized for the individual and people are often only active within of a community at work or in education facilities. So a part of a solution in my view would be establishing more communities that are separate from the family... they might look a lot like schools though, so maybe we should just focus on those? There's more need for new communities to be established for other age ranges.