Aw...cummon...this only came up because the subject of the post was about an English teacher who was having trouble passing a math test.
I'm an English teacher, and I hope I never have to teach math! (My father, however, was a math teacher early in his career.)
I certainly passed the math portion of the CBEST test--and on the first try. I finished my required statistics course--but not handily.
I guess that my point was, simply, that someone can know enough to teach one thing while not know enough to volunteer to teach something else.
:-) I speak in the vernacular most of the time! ;-)