Just for a little context to my previous post, our puppies don't just sit at home. We have a whole very long checklist of things they have to do by 12 weeks of age. It takes tremendous dedication, but is worth it. By 12 weeks old they must have:
Met 100+ people: Tall, short, fat, thin, old, young, white, black, Hispanic, Asian, disabled, athletic, blonde, black hair, wheelchairs, crutches, men, women, kids, loud, quiet, hats, bald, beards...you get the idea. The biggest variety possible.
Had their feet on wood, tile, carpet, linoleum, grass, dirt, water, concrete, asphalt, sand, wood chips, forest floor, pebbles, rock, and any other surface we can find that is smooth, rough, slippery, inclined, lumpy, etc.
Been to the beach, forest, field, lake, pond, pool, store, city, Starbucks, restaurant, loud construction sites, other people's homes, congested intersections, etc. (all while managing the risk of parvo).
Heard silence, birds, wind, cars, machinery, vacuum cleaner, gun shots (shotguns or rifles), surf, singing, yelling, school yards, traffic, etc.
Met and/or interacted with dogs, cats, horses, bunnies, squirrels, cows, goats, birds and other animals at the petting zoo (again, while managing disease risk).
And always get experience in how to play and be with dogs, cats and humans. And they always live in a household with other dogs and cats and various critters.
So puppy classes aren't necessary for us. This is way more work than a puppy class, though. But our puppies become well socialized, fearless and confident. I don't know if all this is necessary for your average house pet, though it would certainly be good. Our dogs all have careers. They have worked in dog shows, hunt and field, therapy, search and rescue, marine rescue, agility and other things, and we want them absolutely bulletproof.