a plethora of questionable material that does not need to be there to teach children the skills they are there to learn.
How exactly is this defined? Because there are lots of books that I would argue "teach children the skills they are there to learn" in my own field that many people would consider "questionable". Ex. Lois Lowry's The Giver
(an excellent dystopian and argumentative novel, that deals with institutionalized euthanasia, illiteracy, and eugenics as well as sending a positive message of rebellion) or, depending on age, Vladimir Nabokov's Lolita
(an excellent psychological study and study in censorship, but highly "questionable" to many people), or anything by Judy Blume (who currently holds the U.S. national record for banning attempts regarding her books, yet most of her books teach about relationships, things like puberty, etc.).
I would also enforce that teachers needed to teach the approved curriculum. If you are there to teach English, you are not there to teach math, and if you are there to teach history, you are not there to teach ecology. That is not to say that teachers should not have some latitude in teaching their classes, but neither should a subject be entirely derailed.
This point is extremely problematic. For example, I teach English composition and literature. Part of doing both involves teaching a smattering of history, politics, geography, philosophy, economics, law (especially re: plagiarism and copyright), science, psychology, sometimes math, and several other things in order for students to fully appreciate, analyze, and discuss a particular piece that they've read. Case in point, it is impossible to teach George Orwell's Animal Farm
without delving into politics, history, philosophy, and economics at the very least. If you don't do so (especially since most high school students who read the book haven't gotten past the U.S. Civil War in history), you've got a bunch of students who think the book is simply about a group of strange farm animals.
Admittedly, most of this happens because the majority of students lack knowledge of common cultural referents and basic history. And that's my experience from teaching at two different colleges (one college, one university) with both traditional (18-22) and non-traditional students (22-60something).