Teaching and tattoos

It's not uncommon for someone to have tattoos and I know many teachers and soon to be teachers who have tattoos. Should schools allow teachers to show their tattoos? Also should school districts be allowed to ask if the person they may hire or have already hired if they have any? I'm only saying this because I know a girl who was asked this during an interview with a school district. I found it insanely personal to ask a question like this.