This is just not true—you are not prohibited from law or policy from expressing your personal political opinions (including on social media) on your own time.
Under state law, school district staff cannot do political campaign work (volunteering, promoting a candidate, etc.) during the hours of the day when the school district requires the teacher to be performing school duties. You can’t do anything political while you’re on the clock.
Well, there are a few more things: you can’t display campaign materials (signs, flyers, etc) on school district property. You cannot “attempt to intimidate, coerce, or command” others on how to vote (Duh!). The law doesn’t address email specifically, but you should not use WCS email for anything political. You should speak for yourself and not the district as a whole.
But your personal time is your own and you get to say what you want. If you think one candidate is great or terrible, say so on a day/time when you are not working!