I've read over my posts on this thread and I know I haven't expressed myself well. I was very distracted last night - ds leaving home (in a good way) and I was a bit all over the place.
I sound a bit smug, which really wasn't my intention. I think the point I was trying to get across - and failing to - was that I'm very interested in grammar, am happy to put in lots of self-study, don't mind acknowledging the gaps in my knowledge.
However , this is not, really, enough. I'm supposed to teach grammar for a test .
However, good my present knowledge of grammar is, there is something a bit bonkers about just instituting a new regime, with a test, from standing, without ensuring: a. there has been training put in place for those that teach the subject, mark the papers, set the papers, b. there is consensus about the subject-content, c. there are resources in place to aid the teaching.
Surely, surely you should roll these things out in stages?
I have so much more to say about this but discretion and loyalty tell me I mustn't post my experiences on an on-line forum.
noblegiraffe , as always, has pretty much reached the nub of what I might say. I have a great anecdote that would either make you despair or laugh, noble - but I don't know that I can share it. 
I'm genuinely alarmed to hear that this is a component of the new English GCSE. I'm furious that my own dc is going to be a guinea pig.