I don’t have an answer to that, but I do have an opinion: English teachers need to have taken at least one linguistics class somewhere along the line, and probably a traditional grammar class to boot.
We’re a long way from that standard:
A few years ago, Syntax in the Schools ran a series of articles on main and subordinate clauses — is the main idea in a sentence usually embedded in the main subject and verb? I shouldn’t have been, but I was surprised when a number of subscribers told me that the series was, for them, incomprehensible because they cannot identify clauses. And these were teachers who want to teach grammar and even belong to ATEG.