In poles, my horses naturally switch to the correct leads. That comes from years of conditioning and sidepassing through poles.
I would not be so concerned with the correct lead. But, I would be concerned with a good stop.
Does your horse know how to rollback? This is the KEY to poles in my opinion. You should be able to stop your horse and turn them around immediately, as smoothly as possible.
This is NOT the best video to go off of because I hit a pole. LoL. But, look at her turns. I make sure to give her a good pocket but once she plants her butt for around the turns, she's basically just moving her front end to complete the turn. She is only inches off the end poles when we are doing our full turns.
It takes a long time to get a good, consistent pattern. I make sure that they are going good and understanding. Once I feel the horse can handle a little bit more, I start to carry a popper crop with me (one that makes a loud pop sound) and once they make the turn, I'll pop them once and get them going again. They usually will shoot forward again. I only do that if the horse is getting "hung up" or lazy in the turn as an incentive to get moving again.
And then I start adding speed. Once the horse can run a good pattern with strong turns, I'll ask them to pick up the pace. But not before that...
I really hope that BubblesBlue posts on here with her poles run from the muddy race a few weeks ago. *wink wink* She is amazing in poles and could offer some great tips.