[caterping]

> > Teaching any controversial subject that a parent decides to complain about? Gone.

> It's not clear to me why this would follow from a lack of teachers' unions.

The union sets up fairly strict protocols that the administration must follow if they want to fire a tenured teacher (the administration can, of course, let go a non-tenured teacher at any time).

The school administration is led by the superintendent of schools -- an elected position. The superintendent gets paid a lot of money and wants to get reelected. If parents complain to the super -- and they do -- then the super wants to placate them to ensure reelection.

Kids are kids, and they exaggerate (and often lie) to their parents about school. Parents want to believe that their child is telling the truth about mean Mr. Teacher picking on them, being too tough on them, grading them too harshly, or assigning too much homework. So parents quite often complain to the principal (who works directly for the super and is not part of the teacher's union), or even directly to the super.