Wearing a one piece bathing suit in school

Today at school well after school I was sitting at the security desk waiting for my ride when a girl with her bathing suit comes over to say hello. She had her jacket on but it was open. She was wearing it for swim. But she was just walking around school with her bathing suit on waiting for the bus to come for their swim meet. But every teacher thought it was inappropriate because basically you see all of her booty.

Do you think she should have had a jacket on walking around school or her walking around in her bathing suit was ok?