I've posted this lots, but both ds1 and dd would have struggled with the phonics test for different reasons - Ds1 because his brain just didn't 'get' phonics for ages, but he does have a very quick memory, which meant he accessed reading by a different route - and the phonics clicked with him around about the end of Y2. He's just got level 5 in his KS2 SATs.
Dd would have failed because, even if she knew full well that 20 of the words were nonsense words, her response to those words at age 5 would have been to cry. So her maximum score would have been 20, despite being an amazing reader (and having a massively secure grasp of phonics!).
Ds2 IS Y1 this year, he is a May birthday and is a fantastic reader, he got 39/40, I don't know which one he got wrong, but having done some of the practice tests, the only ones he might have slipped up on were ones where he tried to make it into a real word, or rushed a made up word (eg Strom read as Storm), because he reads so much that he is way beyond the sounding out stage, and we all sometimes misread a word, through haste. It's no reflection on his phonics (ie he doesn't ACTUALLY think Strom is pronounced Storm, it's just a slip).
Where I find issue with the phonics is that all 3 of my children have to a greater or lesser extent, learned through actually reading books - ds1 learnt ALL his reading through just doing it (he was taught phonics at school, but he basically learnt through his own patent look and say method - eg 'Mummy what does that say?' 'Well, let's sound it out c-a-t, cat' 'ok, learnt that one, on to the next one'. Dd is an amazing writer, she is working at KS2 NC level 5, and is 8 (but in Y4), and this is largely because she reads so much.
And ds2, who is the only one to have gone through with this phonics screening, has amazing grammar, punctuation - because his brain memorises things from books - he uses speech marks, commas, full stops, capitals, colons, semi-colons, apostrophes, almost 100% correctly, because his brain soaks that sort of thing up from the written word. He is the antidote to sitting down and learning these things by rote (which is Gove's logical next step after the phonics, I know it's not directly the same thing), because he just absorbs it by osmosis. As does dd with the language she is using, she hasn't learnt to do that in class, it's just seeped into her through the huge range of books she reads.