well i dont know the laws on this , but I'll give you my experience. I am married to my husband and i have 3 step sons. We share the same last name so maybe it is just a given, but I sign everything - permission slips, registration forms, lunch applications - you name it. I have been open about being the step mom to people in the school, sometimes teachers will ask background or history and i have to explain that i havent been there all 14 yrs, etc..and this has never caused any problem? I think maybe because you are not married and dont share the last name maybe that is why the teacher was on eggshells, but once you are?? Should be fine - despite what that teacher said??