I frequently walk around shirtless at the playground at school
Why are you at the school?
I'm their teacher.
It is important to be dressed appropriately in public. You cannot go around shirtless in a school you could get fired.
I'm a grown up and I wear what I want. People are mad about it.
It is inappropriate to walk around topless in front of kids. You have a great deal of influence on them and you should set a good example.