I think churches have often fulfilled this role historically; but now that job is served largely by colleges (especially those with a high-cachet brand-name). They're a modern 4-year debutante ball: the dating pool is filtered both by age and socioeconomic status, and most students are packed into tight living quarters, maximizing random social interactions and leading to emergent trust/reputation networks. There's a reason that "we met in college" is such a common answer from married couples.
Bryan Caplan and Robin Hanson make sharp critiques against secondary-education institutions, arguing that signaling of grit and conformity is primary, while learning is secondary; but IMO the dating-pool petri-dish aspect of college (often subsidized by parents starting to think about grandchildren) goes under-examined.
Bryan Caplan and Robin Hanson make sharp critiques against secondary-education institutions, arguing that signaling of grit and conformity is primary, while learning is secondary; but IMO the dating-pool petri-dish aspect of college (often subsidized by parents starting to think about grandchildren) goes under-examined.