I have no standing whatsoever to make hair comments, because there's only one way that mine works and that's kinda it (though my hair often disagrees and acts out, but that's another matter entirely).

But I've nailed the "look too young to do this job" routine so well that maybe I have some standing. I too teach, and there's no avoiding the reality, and the appearance, that some of my students are older than I am and look older than I do. Initially this wigged me out but soon I realized that the issue was primarily in my own mind. Yes, classroom discipline was initially harder (and so I had to command respect), one student hit on me (I don't even want to go there), and colleagues figured either that I was hot shit or asked for the University equivalent of my bathroom pass... but it took very little time to iron out the kinks and frankly, I enjoyed flashing my "faculty" badge when folks misjudged. All this is to say, longwindedly, that the distraction in my own mind outweighed the reality.

So wear what you want to wear and do what you want to do -- that is, unless your conducting is so dynamic that you bonk yourself in the face with hair or distract your students with a cloud of hair. :)