The classes will be laid out so there is plenty of room between you and the next puppy. If your puppy is struggling, visual barriers can be used to block your puppy's view of the other puppies until they have settled into the classes.
Your nervous puppy will never be made to interact with other puppies unless they want to and will always be allowed to move away if they need to.
Your excitable puppy will have closely monitored and appropriate interactions with other puppies and will be moved away before they become excited or boisterous.