(Wait, you don't? Here's a great template for a volunteer interest survey from our File Exchange.)
If you want to avoid a clique reputation, you have to use those forms, not file them away until June. What happens often is that groups wait until the last minute to try to get help and -- when stressed -- reach out to the old regulars whose cell numbers they already know and whom they know they can rely on.
That's why you need a rule or system for reaching out to newcomers. It can't be accidental. My advice: At the very least, make sure someone personally calls every new parent who expressed an interest in volunteering. I've heard many times from frustrated parents who say, "I checked the box and then no one called." The assumption then is that your group doesn't really want new help.
We have lots of great resources on connecting with new volunteers:
Good luck!
