I called a trans person a boy and got in trouble in my class.
What did you say to the teacher?
I told her I got a feeling from my source that they're a boy not a girl.
You should just pay attention to the teacher and be respectful in class. You are there to learn not be a distraction.
You are right, it's not cool to make fun of someone who's transgender. I'll go to class now.
If you get in to trouble a lot they might remove you from class. Other kids have the right to be there just like you.