Is this a normal school rule?

I visted a local high school to talk to the principal about arranging a visit regarding some work I'm doing with students for a college course I'm doing. Throughout the whole meeting shes looking at me funny, and before I leave she tells me "head gear" wasn't allowed in school for guests or students... (I usually where a bandanna cause my hair is hard to comb though) When I said "can I ask why?" she says "no" and then she says it has something to do with "safety"... Now I found this to be strange because kids outside where wearing hats....and secondly I had never heard of a school baning something like that on visitors as well.... I have to ask, is this a common rule in schools? Because it seemed really funny to me....Maybe even racist dare I say?