Your last paragraph is where we really diverge.
I don't know if this was case, but if there was in fact a problem with marxist (or La Raza, or fill-in-the-blank) high school teachers (wearing their stupid Che Guevara t-shirts, as I might imagine) hanging certain foreign flags having nothing to do with the curriculum but everything to do with their personal politics, and the Colorado legislature felt it had to adopt a "bright-line" rule to deal with the problem, then it's too bad the law sweeps up apolitical geography teachers who enjoyed permanently hanging a large number and variety of flags, but I blame the left-wing teachers who caused the problem in the first place, and the apolitical geography teacher still does not have the right to simply disobey. The better course for him is, together with parents, to try to get the law refined, and if they are unsuccessful, that's too bad, and will have to use a poster of flags or a book or some other teaching tool. Individual teachers do not have the right to pick and choose laws they wish to follow, that is more of a liberal than a conservative philosophy.
In almost any other case I would agree with you. However, we all know that government moves like pond water; very slowly, if at all. Kids in school don't have that much time. They need to learn all they can in a relatively very short period of time. Waiting for government is not an option when it comes to a child's education as far as I'm concerned. Actually, this situation illustrates perfectly why I am very much against government provided public education.