Welcome to yt!!! We are so glad to have you here!!!!
You are right, it is a good idea to limit your Yorkie's contact with other animals until he has had all of his shots. SO, wait to enroll him in puppy classes. I live in the woods so there aren't any classes around here, LOL, but I would think that in those sort of courses you'd have to bring proof of Rabies vaccination before you can come to class. But, maybe someone else can tell you more.
