Sound crazy to me, but perhaps they've had problems with students either stalking or trying to sue teachers in the past? I don't know, it just strikes me as weird. I know my teacher's home number, cell number, full name, date of birth, wife (I even went to his wedding), hobbies, etc. I've never called him except if he's called me first and left a message, and other than going to his wedding I don't even try socializing with him. So, you can see why I think hiding personal information is a little odd. As for my other teacher, I know her real name, cell number, phone number, home address, husband, have taken care of her cats, have been to her home, and might even go into business with her.
Does your studio not trust students and teachers to act like responsible human beings?