My 14 week old pup gets distracted when out in public and does not mind. When can I start correcting this behavior?

Dear Mr. Frawley,

We have 5 of your videos and just received 5 of your leashes. Thank you for the quality products that you offer.

We have been teaching our 14 week old puppy using the marker training outlined in your videos with GREAT success. The puppy minds 95% of the time in the house. However, every time I take him out in public, he gets very distracted and does not mind, doesn't seem to even hear me or my commands, requiring that I go to great lengths to get his attention. I'm thinking it's normal for a puppy to be this distracted and that he'll naturally grow to be less excitable and more focused as he matures (tell me if this is wrong). For now, however, I'm not clear on how to handle training under distraction.

So my questions to you are: 1) at what age should a puppy enter the distraction/correction phases of training? 2) Until then, should I simply refrain from giving commands to him at all in distraction environments? Part of me says, I should continue training him and exposing him to distractions. Another part of me says, if I give a command that I know he's too distracted to obey and I can't in fairness correct him b/c his mind is not yet mature enough to focus under distraction, am I not setting him up for failure and tainting the command by making it optional?

Thanks in advance for shedding some light on this dilemma for me. Along the same lines, at what age is a puppy ready for the tree stump and formal heeling work demonstrated in the Tom Rose video?

Thank you
Mindy