>> High school bullies are typically quite good at restricting their bullying to times when they're unlikely to be spotted by an authority figure.

> The author is being unfair when she is holding the teacher solely accountable for bullying.

Come, now. Yours is not a reasonable conclusion to make from the blog post. It should be obvious to the reader that the bullies in question are responsible. The author's point was that the teacher shares responsibility in providing a safe environment for all students in the class. Perhaps you don't agree (and what a shame if you don't), but you should not misrepresent the author's argument to make your case.