So I took my little guy to his first puppy obedience training class yesterday. He's about 7 months old and a few months older than the other pups in class. When we got into the room, he started drooling profusely, his ears were back and he had a very terrified expression. He drooled through the entire class. It's very strange because we take him to the dog park often and he plays well, though he is nervous at first when he meets a dog. He does typically play with much older dogs though - what's up with the puppy anxiety? And what do I do when my dog is nervous like that, other than wipe up the drool? Good news is, when we let them off their leashes, he played well with the other dogs and even got down to the smaller dogs' level, but just sitting on his leash in class seemed to terrify him!

I doubt that the dog was afraid of puppies, but of the environment in general.
A group of dogs (at any age) and their owners in a confined space, in a building or outside, with everyone standing around wondering what to do, is VERY stressful.
It was not the age of the other dogs in the room. Obedience is stressful, most of that is simply the classroom environment itself.
That's great, make the dog get used to it.
What NOT to do: Cuddle the dog, praise it and tell it how wonderful it is (that will only reward the negative actions).

Instead, just act normal. Like it's no big deal. The dog can read you and will react to the stress level you have as well. The more you worry, the more it worries, and so on.