Paddianne
Perhaps you never taught in a school. I did, and schools have dress codes for staff as well as children. Perhaps you didn’t know that.
My normal has nothing to do with it, but societal norms do!
Schools reflect societal norms, not individual preferences.
This person is pushing the boundaries. Out of school, pushing the boundaries is fine. In school, it is not! This person is showing a total lack of respect for the school he works in, the children he teaches, and their parents.
In all likelihood the headteacher is afraid of appearing in the national press, should he/she challenge this unorthodox behaviour.
Because that’s the world we live in now.