I was amazed that my son's Kindergarten teacher went by her first name with her students! Sometimes the kids called her Miss Firstname, but mostly they used her first name. That was really common in my area; all the teachers went by their first name.
I guess it's not a huge deal in today's society, but when I was growing up our teachers were on a completely different level. I called my teachers Mr. Tozzi or Mrs. Ilgner, and they were adults. I called my piano teacher Mrs. Lee, and even today when I visit her I have trouble calling her by her first name! But things have definitely changed because I taught at university one year, and the students all called me by my first name. I thought that maybe they were going to call me Professor Bee haha!
Did you call your K6 teachers by their first name or their last name?