I agree with you and, yes, there are plenty of kids out there who are not "professional" who should be. The point here is that so many of these kids are being turned away because of their professional credits. Not even given a chance. It has nothing to do with who is the better candidate and who auditions stronger. It is about kids who are automatically cancelled out because of professional credits. Seems so many high school directors are just assuming that these kids have had or will have other opportunities and don't need to be cast in their school musical in bigger roles.
As we all know, that is not the case. Every audition is another experience. There are no guarantees. And even highly professional kids still want to be part of their high school. No matter what the talent level is.