I took Snickers to both the AKC S.T.A.R Puppy class and the Canine Good Citizen class (on the same night, since he is a rescue I could only approximate his age and was not sure which class he should be in). He already knew all of the commands needed to pass the class, but his struggle was/is that he is a bit hyper-active at times (being a Yorkie puppy, I guess I could not expect much less
) and he really needed the experience of learning to properly socialize. I taught him most of the obedience commands he knows from reading books, reading different websites and watching youtube videos. He also knows a fair amount of tricks, most of which I got the ideas from youtube. I found obedience classes helpful for the social aspect. Especially since my dog has a quite a dominant personality, he needs to practice getting along with others.
He already knew what to do, but getting him to focus in an environment with lots of new and different stimulus that would distract him is a different experience and sometimes, challenge. I also really wanted him to get his Canine Good Citizen, which was my other motivation. (I really didn't think he could calm down enough to pass and thought we'd have to re-take it when he was older and less crazy...he's still such a puppy...but he did! And was the only one in the class who passed! I was really, truly shocked!)