What kind of classes were you looking at? The vast majority of classes could careless where you got your dog or what breed they are. Just that you love him and care enough to go that extra training step makes you a more responsible dog owner in my book!
BTW, he's beautiful
Agility classes are wonderful.... but so is rally, flyball, herding, tracking, scentwork.... so you have a huge choice topicwise.
Hey, this one has GSD's in the picture on the front page!
Home - Pals and Paws Agility Club
Dog Wood Park | Classes
Those should get you started! Good luck