"You do not have your riders compete in shows. How can you possibly gauge the success of your program?"
I think that there are better measures for the success of a riding program than show ribbons.
I think the evaluation is pretty simple:
1. When your riders are small do they come to you with the fears that paralyze them?
2. When they are a bit older do they come to you with the dreams that inspire them?
3. When they are young teens do they come to you with the plans that drive them?
4. And after they grow up do they come back to you for help with the problems that are facing them?
If the answer to each of these questions is "yes" then your riding program is succeeding.