I've been thinking about what cleaty asked - about how we really raise standards - for the long term, ie at the end of as child's educational journey, rather than 'optimising their performance at each tiny step along the way to the detriment of the whole'.
Counterintuitively, I think it would be best done by teaching less, better, so that every child has an absolutely secure foundation onto which extra skills and information can be relatively quickly grafted.
What has happened is the reverse - children have been observed to do something not particularly well at 16, or 14, so the call comes 'we must teach them to do that before they are 11, by adding more to the pre-11 curriculum'. However, what happens is that much of what children learn they learn 'too young' - when they don't 'need' it, when it isn't part of their everyday experience, when it is a 'trick' rather than something done with real understanding. As a result, they don't retain that learning for any longer than the next test, and then it is rapidly forgotten.
If instead we concentrate on teaching 'once and once only, but really thoroughly, and when it is appropriate', then it is much more likely that children will retain and use what they have been taught. I'm sure that I'm not the only teacher who has been teaching modal verbs to children who confuse there / they're / their; column subtraction to those who can't instantly subtract a single digit number from a teen number; subordinate clauses to those who don't reliably use full stops. And I know why that is - not because they haven't been taught those basic skills, but because teachers in every previous year have felt the pressure to 'move on through the curriculum, we've got so much to cover' rather than really, really embedding those basic skills and making them important, not the 'shiny new extra stuff'.
I didn't have a formal science lesson in primary school. Nature study, yes lots. Class caterpillars? Of course. Nature walks, visits, plenty of time to experiment with torches and mirrors and sand and water. But not a single lesson called 'science'. 4 years later, I took 3 Science O-levels - because when I was formally taught Science, I had lots of basic practical awareness of the world around me, a great curiosity about it, and was also of an age and skills level to be taught all the concepts properly, formally and, where necessary, mathematically.
I do think by 'emptying out' the primary curriculum, and teaching things 'right first time so we never have to revisit them' and at an appropriate age, children's retention of the really key aspects will be hugely improved, and will become really embedded so they won't 'hit a high point in Y6' for the test and then be completely forgotten in the course of secondary school.