I would say that if your students are older than 4 or 5 years of age, they should be using your last name, not your first name, unless the policy or custom at your school states otherwise.
I grew up in the Northeastern USA, and there it would be considered highly disrespectful for any child of any age to use any adult �s first name. The proper forms of address, Mr., Miss, Mrs., or Ms. with the last name, would be expected in all cases. This is true in most US regions, with the exception of the Southeast.
For anybody who is interested in the customs of the Southeastern US, the following factors seem to determine the acceptable use of adults first names by children. These are based on my personal observations having lived in Maryland for 20-some years, but there may be variations of what is acceptable in other parts of the South.
1) The age of the children: Sometimes very young children (up to age 4 or 5) in various parts of the US, not just the Southeast, call their teacher Miss or Ms. with the first name, especially if it �s in a daycare setting or a preschool that is a separate facility and not housed in an elementary school that is also for older children.
But from kindergarten or first grade on, it �s Miss, Mrs., or Ms. with the last name.
A teacher �s preference is usually indicated by how it is posted at the classroom door.
Example: The teacher is Kathy Smith. A sign by her door might say, "Welcome to Miss Kathy �s Room" or "Welcome to Mrs. Smith �s Room."
Mrs. is never is used with the first name, only with the last name.
2) Locality and Familiarity: Primarily in the Southeastern US, it is common for children to address their mother �s friends and neighbors who are close to the family as Miss or Ms. and the first name. Example: If Rita Anderson is my good friend or lives in our neighborhood, my children call her "Miss Rita" or "Ms. Rita." Her children call me "Miss Pam" or "Ms. Pam ."
In some cases, this also could be done with women who may not be close personal friends of the parents but are seen on a regular basis in a child-oriented setting, such as a nurse at the pediatrician �s office or a dance instructor. Often the acceptability of this will be cued by the adult speaking of herself in the third person and using the first-name format. Example of a nurse speaking to a child in this way: "Now Miss Beth is just going to take your temperature, and it won �t hurt a bit." Once this has been heard, it �s okay for the child to call the nurse "Miss Beth."
3) School Setting - However, if the adult friend is a teacher or classroom assistant, the formal version still would be used in school, especially if the child is older than 4 or 5.
Example: If Amy Jones is my friend or neighbor, my children would call her "Miss Amy" in my home, in her home, or if we meet in a public place, such as the grocery story or at a community event. However, if, in addition to be a family friend, she is also a teacher in their school, they would call her "Mrs. Jones" when they see her at school and "Miss Amy" outside of school.
4) Gender and Hierarchy: I live in a rural area, and while the first name form of address is more commonly used with women, it sometimes may be used w/ men who are close friends of the family or have a community role with younger children, such as a Cub Scout den leader or Tee Ball coach.
Example of child speaking to the father of his best friend: "Thanks for taking us to McDonald �s, Mr. Dan.
However, I �m not sure if that is true for men in all areas of the South.
In our community in a sports setting, the head coach would be addressed using the last name format, while his assistants may sometimes be addressed in the first name format, especially if younger than the head coach.
Example of child speaking: Mr. Smith is my baseball coach, and Mr. Jeff and Mr. Ricky help us at practice, too.
But in the school setting, all coaches are addressed in the last name format, especially when they are also teachers in the school.
An exception to this might be in a high school setting when former team members just a few years older than the players have returned to their alma mater as assistant coaches. In this case, these young assistants are often called just by the first name w/out the Mr. attached.
Example of teenage baseball player speaking to a young assistant coach, relaying a message from the head coach: "Hey, Dave, Mr. Brown said to ask you for help with my swing."
5) The preference of the adult: When people move into our area from a more northern or western part of the US, they often are offended by the over-familiarity of the first name format. So I always taught my children to use the last-name form of address with new adults unless invited to do otherwise.
Example: If Mary Smith is new in the neighborhood, it �s best for the children to call her Mrs. Smith unless she says something like, �Oh, honey, just call me Ms. Mary" or refers to herself in the third person as Ms. Mary, similar to the the nurse above.
ie., Mary Smith is babysitting her neighbor �s children for the afternoon, and she might cue the children by saying something like, "Now you go and play Legos, and Miss Mary will call you when your snack is ready."
