Once again I would like to suggest that any cis kids or parents of cis kids who have an issue with this (which should be all parents) start doing malicious compliance when this becomes law by "registering" even your cis kids' nicknames with the school. Make up a new one every week even. Make this policy intolerable.
That said, teachers please resist this by using trans kids chosen names instead. Malicious compliance on your part will only hurt them.
Also, they are probably going to have to use the notwithstanding clause on this (which, sadly, they probably can but I hope I'm wrong about that) because it is *literally stripping people of their rights*. Parental rights are not a thing. Children have rights. Teenagers have rights. Trans people of all ages have rights. Parents have responsibilities to their children.