:In this case, I was a little over
: impressed with the lead, he informed me he was an adventure racer
I get leery about paddling with self-proclaimed "racers". I'm not an instructor, and when I'm initiating a trip I tend not to call myself "leader" (more of an "instigator" 
) So I rarely try to manage a group.
But I've noticed racers tend to be focused on their own trip and only pay attention to other paddlers to make sure they're still "ahead of the pack". The farther ahead they are, the better. Yes, I'm over-generalizing here. But a race mindset is a different thing from an "assist the group" mindset.
Also, it seems common for a student to feel "I'm not a fast paddler yet. I don't want to hold the group up, so I'll press as hard as I can".
Seems to me that a better position to assign to a racer would be sweep - they won't get ahead of the group and yet may be more likely to have the speed to catch up with someone having problems.
You obviously did enough of the "right things" on this trip - everyone got back unscathed. Thanks for sharing so we can all learn.
Val
