Here's an article from a credible source that you can show your breeder or veterinarian regarding the benefit of early (as early as 8-9 weeks of age) socialization, including puppy classes. I find that too many people are waiting until pups are 4 months old before coming to class. By that time, the pups are already pulling on leashes, not coming when called, being scolded for "accidents", and not learning to inhibit their bites.
[link
http://www.diamondsintheruff.com/RKanderson.html]www.diamondsintheruff.com/RKanderson.html[/link]