Eveyone in the UK should get a good education
Key word there is should.
There are the occasional extreme circumstances when it doesn't happen, but a good education is on offer to almost everyone
An education, but a good one? My DD had a shit show of a secondary school until year 10, and then another board took over, they honestly worked miracles to get the kids as good a grades as they did in such a short time, but we were warned that they had missed so much, in the time left they were limited to what they could do.
Of course, not everyone engages in it
No, they don't, but then even the most driven student can't engage with something that's not there. The new board offered before and after school sessions in all subjects at yr 10 and 11, my DD went to every single one, she got an award for it. But the failings in her earlier education and the fact that they couldn't cram 5 years education into 1 and a half is having an effect still now going into second year a levels and missing knowledge from school.
It's the only school available, I was refused a place in a different catchment area that was better, I can't afford private education (as in I don't earn enough to even just pay the fees, not that I prioritised different things) I couldn't afford to live in the catchment area of the better school.
So my DD had an education on offer, and she engaged with it, but ultimately if that board hadn't changed when it did and she had the opportunity to engage then she'd likely not even be doing the courses she is now to try for university, because she wouldn't have had the grades.
And she had the advantage of a supportive family and a laptop, WiFi and resources, and being able to study. Many children she went to school alongside didn't have that.