The problem is twofold, shortage of maths teachers and it's so badly taught, or it certainly is in the state sector, maybe that isn't the case in private schools. When our children were at school in the 90s and the noughties, particularly in junior school, there never seemed to be any consolidation, so different topics for example, fractions were skimmed over before it could be properly absorbed, there was a flitting about, few days on that then on to the next thing. When in a roundabout way returning to say fractions, more often than not, much had been forgotten from when it previously came up. I seem to remember when I was at school we seemed to spend what seemed like an eternity on the basics thus inculcated partly by rote and partly by fear of getting whacked (not good) By the time my kids were in their pre GCSE year, and they went to what would be considered a very good comprehensive, it became apparent they would need some private tutoring to get them through the exam. My first port of call for advice in this was their maths teacher who breezily announced "oh yes so many of them here get Mr so and so in to coach them privately" Mr so and so being a very able science teacher who was adept at coaching in both science and maths. So after school he could be found in many a pupil's kitchen or dining room. He was the person I approached and he was well worth the £25 an hour, as it was then, and the packet of something like chocolate Hob Nobs he also requested as part of his fee.
Maybe Rishi could implement a better way of how the basics could be taught, possibly he has no idea as neither he nor his children have been through the state system (where the majority of the population are educated) If he did, he might have more idea in what is lacking as regards to the teaching of some of the elementary stuff, rather than ramping up the requirement to study the subject until 18 as many pupils I imagine have been turned off it long before they reach that age.