Boy, Girl, or Other?

I normally do not go inside the bathroom with the child, I wait out in the hallway while the girls finish up and line up in the hallway. Today after being sneezed on I decided to sneak in and wash my hands at one of the 3 sinks. The following dialogue took place

Child: "Teacher, you cannot come in here!"

Me: "Why not?"

Child: "You are not a girl!"

Me: "What am I then?"

Child: " You are a teacher!"

Other child: "She is a girl and a teacher!"

Child: "No she is not!"