Education is complicated. Essay follows, sorry!
OTOH, the 1947 Education Act gave all children a free education from age 5 to 15, with the last four years in a secondary school. (Previously the school leaving age was 14 and most children had their entire education in an elementary school with no specialist facilities or teaching for science and so on.)
The idea was to divide children at 11 and send the ones with the most academic aptitude to grammar school, the ones with a more technical bent to technical schools and the majority would get a sound, broad-based education in a secondary modern school.
In practice the technical schools never materialised (lack of money, I suppose) so we ended up with a two-tier system. Private schools still existed too, so the great class divide was not eliminated by the new system, as many had hoped.
Middle class children had a huge advantage because of the way the 11+ test was worded. Even so, many working class children did pass it and get the chance to go to grammar school.
But:
- It wasn't easy being a working class child in a grammar school and many children who did go left early because they hated it.
(a) Many were bullied from snobbery - patronised at best.
(b) In many families there were tensions as children were taught that they needed to move up in the world and leave their working class roots behind.
(c) Even for those who did go and do well, there was family pressure to leave and start earning so they didn't always fulfil their academic potential by staying on to do O and A levels.
Also, of course, it was more expensive for children to go to grammar school because of the uniform and travel costs. Not all local authorities reimbursed those costs so some families just couldn't afford to take up the place.
- It wasn't wonderful for middle class families either. (This is the clincher, and the reason why we no longer have the 11+ in most of the country - there was political pressure from the middle classes to abolish it. It's amazing how quickly people have forgotten this now.)
(a) Social mobility means some people go up and others go down. Middle class families have more means at their disposal to avoid going down. Children who didn't pass the 11+ would go to the secondary modern, and those schools were rarely as well-funded than the grammar schools, with very limited opportunities to do exams. A few kids were able to transfer to grammar schools at 13, but that wasn't easy. So middle class families often sent their children instead to private schools. This undermined the whole aim of the 1947 Education Act.
(b) Many middle class families were very angry about this because of the cost, or because they were middle class but couldn't afford fees, so they lobbied MPs to change to a comprehensive school system. It was of course especially painful when one child passed the 11+ and another one didn't.
- Secondary moderns weren't great, but to be brutally honest neither were a lot of grammar schools. Some of them were marvellous, many individual teachers were great, but there was so much snobbery! Many of them slavishly imitated the public schools, for no good reason. Their teaching was often very old-fashioned and rigid. Narrow curriculum.
The great hope when comprehensive schools came in was that every child would get an education that suited their particular talents. The child who was brilliant at English but hopeless at Maths, so would never have passed the 11+, could now be in the top set for English and get support to do better at Maths. The child who struggled with all academic work could now get support and not have the stigma of being an 11+ failure. The super-bright child who would have sailed through the 11+ could still get a good academic education but if she chose to could end up doing vocational qualifications that the grammar school wouldn't have offered. (And if all those children were from the same family, they'd all move on to the same school.)
In practice, that proved to be a huge challenge, of course, and in the last 20 years in particular we do seem to have moved in the opposite direction. One size fits all, target-driven. Not great.