Wow @homeEd2021 that's quite a bitter post. It sounds like you've had a pretty bad experience. I'm sorry if the rolling of the eyes offended you, but we really do hear from parents very frequently about their 'gifted' children - yes, perhaps a small percentage of those are truly gifted, but the majority are just quite or very able.
To address @HighRopes question seriously, there are two answers really. The first is that a school can do lots of things to make learning interesting for the very able. If you have a very selective school and then add some setting into that mix, then your top maths set (for example) is going to be really very good indeed (I saw some Y9s getting very excited about doing some Y13 maths for a laugh this week). We always have subject specialist teachers, which should be a given but sadly isn't. Teaching skills always come first, but plenty of our teachers also have Oxbridge degrees, doctorates etc - they absolutely love having super able students to keep them on their toes. As a PP said we have lots of curricular freedom in KS3 to teach what we like. Less so in KS4, but in some subjects we can burn through the GCSE curriculum pretty quickly, leaving plenty of time to teach off piste. We have loads of subject-based clubs, to give those who are interested and talented the opportunity to really get involved in their subject and push the boundaries. We enter lots of competitions - the maths olympiad is the most obvious, but also things like translation competitions, international science competitions and so on.
The flip side of all that is that we deliberately don't do some things. We don't allow early exams and we try not to let one subject totally dominate a pupil's time at the school. That's absolutely not because we want to 'take them down a peg or two', but because we think it's good for students to get involved in lots of other stuff alongside the things that they're particularly talented in - so we still want them to have time for music, sport, debating, art, drama, community work, or just generally having fun and hanging out with their mates.