The problem is it's not just the kids with supportive parents who are capable of 11+ who have to sit this paper. It's the thousands of children who struggle to get to school, it's the children who's parents can't punctuate a sentence, never mind help them with subordinating and co-ordinating conjunctions, it's the children with dyslexia who get absolutely no consideration for this (the test also consists of a 20 word spelling test, a severely dyslexic child can expect to get 1 or 2 maximum, they'd have to get near enough full marks on that paper just to be considered working at y6 level, never mind those who are highly able and should be working above but won't be judged as that solely due to having dyslexia).
The question isn't whether children CAN learn this, of course they can, it's whether they SHOULD be learning this. Surely better to spend the time on times tables, the arts, even playing a good game of rounders, rather than learning what the past progressive tense is?
It's also worth making the point that children with poor handwriting (or in fact even just children who print rather that write in a joined up manner) or children who cannot spell (hitting the dyslexic children again) can now NOT be judged as working at the national level for writing, even if the rest of their writing is absolutely outstanding. No compromise, no common sense.