I think the fine is excessive and that it violates Amendment VIII.
Not only is it excessive, the argument could be made that it is compelled speech if teachers do not want to teach about Harvey Milk. Compelled speech is a first amendment violation. I am not sure where the line gets drawn tho. For instance, is forcing teachers to teach math compelled speech? It seems the norm for teachers to not teach math these days, or something that resembles math as you and I know it.