1. Would you want to be a student in your program?
2. How many hours OUTSIDE of school are required for your students?
3. What is the financial cost for a student to be part of your program?
4. Is the environment safe, fun, interesting, and rewarding, (and no, I don't mean you have to put on a show but education can be fun. Are kids enjoying rehearsals with smiles and a little laughter or do they leave looking like they've been beat up or half asleep because they played 5 minutes in a 55 minute class - that was one reason why my child left band)
5. Are the kids seeing real-world application and performances or is it all rehearsals for a few performances that mean more to the director than the kid?
6. Are other organizations losing kids at the same rate?
6.a. If yes, then it's a community or school culture issue.
6.b. If no, then look at those organizations that are keeping kids and figure out what the differences are.
You might not like the answer and you might decide quality over quantity is ultimately better. Neither answer is wrong. As a younger director I took quitters personally. When I did some soul searching I found sometimes it was me and sometimes it was them. I worked on the me stuff I could control and after that I quit taking it personal. Some kids aren't meant for band. But on the way out the door I NEVER made the kid feel any different than any other kid that came through my program. In fact, at the end of the year when I'd do placements I would ask the students if they were planning to be in band. If not, I would ask what they were going to and always encouraged them to do something, even if it wasn't band. We'd shake hands on their way out the door and I'd wish them the best. And sometimes, I let kids come back when they realized they'd made a mistake.