Beginner Agility Starts

We took the Puppy Foundation For Agility class last year. Keeley really liked it but then he hurt he his foot somehow and had to be on "limited activity" for a very long time while it was healing.
Tonight we went to our first Beginner Agility class. The hardest part about agility for Keeley is his concentration and waiting his turn. The actually obstacles are a piece of cake. Tire, Weave, Jump, Tunnel, Bench.... these things are easy for Keeley. In fact he does them without putting forth any effort. But his lack of concentration sometimes gets him into trouble. He even trips over his own feet because that's how little attention he's paying to what he's doing.
He also likes to make his own course. I'll say "tunnel" and he'll go thru it just fine but then he'll turn around and go back thru it and then forward thru it again. And then he'll do some jumps and jump thru the tire and then back thru the tunnel. It's ridiculous. I guess he's a typical terrier with a mind of his own. He just wants to go full throttle and doesn't want to wait to be told what to do next.
Keeley's other major problem is waiting his turn. He can't stand to watch the other dogs practicing something. He lunges and barks as loud as he can. He pulls hard and tries to wiggle out of his collar.
The worst is when another dog has difficulty learning something and needs extra help. It just drives Keeley crazy.