Sqad...I can only speak from my personal experiences...see my post of 23:16 last night.
We just didn't have the best Teachers, the equipment and the facilities in my Secondary Modern. Some subjects just weren't taught. We didn't even do A levels, thus the paucity of Secondary School kids at University. We were divided, unequally, at age 10-11, and that was that. We became the carpenters, plumbers, etc, and the kids that went to Grammar School all went on to Uni and got the top jobs.
Of course, there is nothing whatsoever wrong with being a tradesman ....when you come back from holiday and find water cascading down the walls from your attic, a plumber is more use to you than say, a surgeon might be ( ! )
My point is that we didn't get a choice. Bright kids at the Secondary Moderns were effectively ignored. Some managed to come through but most never achieved their full potential in life.
There are some people in Britain that say that Comps destroyed British secondary education. This is rot. All the schools in my home town here in South Wales converted into Comps, Grammars included and the bright kids continued to thrive.
If you entered a Comp at age 11, and you were bright, you could have ended up in the top class and stream by the time you were 16...there was no barriers to progression. You just moved down the corridor a few feet.
Comps have been the biggest single reason that a larger proportion of kids went to Colleges and Universities. Oxford and Cambridge have been criticised in the past, on many occasions, for not taking in more people from humble backgrounds. But before the advent of Comps, there were no working class kids punting down the Cam, or leaving their bikes outside venerable Oxford colleges. ( with then exception perhaps of Ruskin College).
I would guess that you went to a Grammar Sqad...would you have gone on to be a Doctor, if you had attended a Secondary Modern ?
( I would be delighted, of course, if you were to tell me that you graduated from the Bash Street School ! )