Puppies do have short attention spans, but when you work on directing that short attention span to you, you might find training to come a little easier.
Think to yourself what you can do to be more interesting, and to maintain the attention. Attention from a dog is not 'given' to a handler, the handler has to work it.
When I am in class, anytime we are between exercises, I am doing little things to keep and maintain motivation - little touches, puppy pushups, watch me games, just 'stuff'. These little things that I do, are what sets me apart from a novice trainer, in that I don't expect my dog will sit quietly while the intructor is talking, and then I am going to just 'turn them on' when it's time to work. I start to 'turn them on' while we are still out in the parking lot...get them interested to work, and get them interested in ME, and keep them interested in ME for an entire hour.
It might help to ask yourself what are 10 things you can do at class, that will make Murphy pay attention to you. Work them at home even though you don't *need* to, and then take those activities to class and see if there is any improvement.
And if you can, attend one advanced class as an observer. If you can watch 'experienced' trainers, you will see the difference between what they do that you could improve on.
Happy Training!
-Renee