With the trainers we've gone to, their actual obedience classes were for dogs 6 months and up. We actually wanted to enroll Kai into puppy classes but he was too old by a week. It was just chaos trying to control a young pup in a class full of adult dogs barking.

I think it'd be safe to go after all the shots are taken care of. But even then, you'd have to keep him close to you. The bigger dogs might not know how to handle such a small pup.