Off topic, but what exactly is the philosophy behind having first graders call adults by their first names? That WOULD put me off the idea of the school, I'm afraid.
They don't consider the name thing to be key to their philosophy, it's just a very small part. The school is designed to be an extension of the home. Much like my home it has really only one rule, basically it's to treat ourselves, others, and property with respect. The teacher and other non-teaching adults have authority (and don't need to be called a special name to designate that) but in general are expected to be treated with the same respect that should be given to everyone (adult or child).
My children use first names for most adults in our lives (as I did when I was growing up). It certainly didn't have any impact on my respect for others or for authority so I'm comfortable that it won't impact theirs. I also found for me it made the transition to adulthood a lot easier. It's a lot easier to be treated as an equal when you use equal names.
My DH did have the same concerns until I reminded him that he didn't show any respect for his teachers despite calling them by their surname (we went to school together so I know
If in your home you expect all adults to be called by their title and surname then it wouldn't be the school for you.