This all seems to turn on whether the teacher expressed an opinion of a proposed policy or went farther and expressed a firm intent to deny any student their chosen name. Since I didn't read a detailed report, with a transcript, I can't tell which. My initial point, long ago, was that one can err on the side of free speech and then, if a teacher violates school policy and parental wishes, make a firing decision at that time.
And giving less ammo to the Right to turn things into a culture war.
Naming all children Pat or Leslie would save a lot of future headaches. (j/k)