No - I went to a comp and Cambridge. My three went to comps and two are at good unis, one is doing A levels now and predicted excellent grades.
I think if you are smart and put the effort in you should do fine anywhere. And learning to work independently is a big part of what secondary education is for - academically able kids should not need small classes and loads of attention once they are over 11 because they should be able to just find out what work is set and get on with it. I have very low tolerance for kids complaining about disruptive children in class - OK another kid is behaving badly. That's between them and the teacher but it's not your issue. Your issue is ask what you are meant to learn, after the lesson if necessary, and make sure you learn it. You can do it at home if need be. Don't moan that X was talking and that stopped you learning - because in the rest of your life there will always be someone talking and being a pain and you still have to ignore them and do your job.
And if they are smart but don't put the work in they need their parents to give them a kick in the pants (not literally) rather than special treatment. I'm not British though and in my culture the attitude to education is much more - get on with it. Schools are more basic. There's no tolerance of answering back to adults.
I am waaaaaaay more liberal than my own parents were but I was always clear with my kids that my job was to ensure they get everything they need to study - books, time, computers once they needed them. But its their job to study and no dicking around with that.
I think it is different if a child is being bullied or has unmet SEN. I'd never judge anyone who decided to move an unhappy child urgently if the school or LEA wasn;t acting fast enough to help. But otherwise I would strongly recommend teaching children to harden up. It saves a lot of money!