I loved Maths and was distraught to end up in the class with the "special needs" class. Through the first year I was head and shoulders above the rest but got a reputation as being disruptive as I kept asking for something to do while the teacher ignored me and helped those that were still working. This happened in virtually all subjects. Then she didn't pick me for the Local radio maths quiz which really wound me up. A week after she made that decision we had the basic numeracy test (that old 60 minute no calculators allowed thing) and I was finished in 40 minutes, Had to sit there for the other 20 minutes of course.
The whole (top) class was trudged across the county to another school miles away and the person chosen that should never had been there instead of me buzzed in and got the last question wrong. Of course I knew that answer

A week later the numeracy test results came back from EMREB and I was the only 100%. 100% in 40 minutes. Those on the quiz team that should have been there got 96% to 98% while the one that shouldn't have been there got 89%
And that sent me over the edge legging days off school, just biking around the parks, shoplifting for the buzz etc.
The quiz thing wasn't what sent me over, it was the cumulative of being constantly ignored or overlooked just because I was more able and for years I resented every teacher in that school apart from my Latin teacher and the special needs teachers that were so happy to have a clever kid in their class and enabled me to at least be able to take the "intermediate" level of GCSEs which had a maximum C grade. It wasn't the same exam for all streams. If you were in top class you got to take the higher exam which was the only one you could get As and Bs in. The intermediate was a C max and by rights being in the special needs class by then I should have been taking the lower exams which I think max grade was a D!!! Those 2 teachers fought my corner and with a lot of begging I was allowed to take the intermediate instead of the foundation. They were proper old school teachers thought that were very disciplinarian and welcomed my requests for more work from the start normally giving me twice as much to do at the start. As it was special needs it was also not a set day of work. Each student was doing tailored work in those classes.
I think this system is still in place although now it is only higher tier (A-D) and foundation Tier C max.
As you can guess by the time I reached 16 and did those exams I was finished with school and left. Got a job within days as a trainee accountant for a local firm and was earning £14k by the time I was 20. Very good wage at that time (1995.) Failed all my financial accountancy exams and passed all my management accountant exams. That being because I was working in management accounts and I struggle to learn anything through theory whereas I can pick up most things if given the opportunity to do it practically. We never had computers at school yet I was writing Access databases from 96 - 2000 by blagging a job using access and very quickly learning it on the job. Comp school "ruined" me if you like because it did not push me and that causes problems. Clever kids MUST be challenged or they become bored and if they become bored they can explode into rebellion and resentment.
Doesn't help there was no such thing as ADHD or Aspergers back then, If I have it that is, because back then you were just a disruptive child and needed a good caning or the plimsoll across your hands a few times to get you back in to line.
My boys are being pushed by me and their school. However other kids on this estate don't have parents who willpay/put the effort into getting their kids across town and if there was a selective process then the brightest ones would be given free transport rather than told "tough, the local 50% pass rate Comp is the nearest."