I'm a young teacher (24) and my grade level chair is old enough to be my mother (she's said her youngest daughter is 35). We've always called each other "Ms. <full lastname>" whether the kids are around or it's just the two of us working in her classroom. Today, however, she's starting calling me "Lynn" (not in front of the kids of course, but before and after school). It doesn't bother me, but it's kinda odd because she never asked if it was cool, she just started doing it. Is this an unspoken teacher rule that means I am supposed to call her by her first name? Since she's older than me, should I perhaps call her either "Ms. <first name> or maybe Ms. <first initial>" Or just continue to call her "Ms. <full last name>" unless she says to call her something else?