I didn't say obedience schools that your friends run. I said good places to train/socialise a young dog are:-
1: Obedience Schools
2: Friends Houses
As they are more controlled environments then a park, vet or public place. Less chance of diseases.
ETA - i don't know where you are based but if you google search obedience clubs or group dog training in your area, I am sure there are a few around.
Personally I use Urban Dog Training in Brisbane. They are not an "Obedience Club" as such they are a privately owned company run by Behavioural Dog Trainers. So a bit different to your conventional obedience but I prefer it.