Happyhippo that's fine I was just responding to a PP who suggested this (middle-class intake anyway) was what you seemed to be looking for. I do find the whole London schools' social makeup thing fascinating, and how it correlates to function and attainment . . . maybe I should do a thesis on it! (wouldn't be the first I don't suppose).
Comps by definition are mixed so there will nearly always be some kids, studious and motivated, others, disaffected. Bullying is a question of how well it’s managed - there are kids in every type of school who will try it on if they can.
I think in any ofsted good or outstanding comp - and there are many if not most in London - there will be excellent teaching and a fair number of kids who are high-achieving and proud of it; enough for your child to join them . . . there are a couple like this round here (virtually 100% BAME, zero white-middle-class) which do pretty well and are full of those fairly impoverished but very aspirational immigrant families. White middle class parents might be anxious about their kids fitting in socially (in fact I know they are) but they have no grounds for worry about academic attainment - and my personal view is that their over-protected kids would learn a great deal from moving, with full parental support naturally, out of their usual social comfort zone. (Black Lives Matter, anyone?)
These schools are very rarely mentioned on these threads or genuinely considered by Mumsnetters - yet they are great schools, many of the kids brilliant and lovely, and much of the teaching fantastic I believe, far better, probably, than at some complacent leafy place which knows most kids will be privately tutored anyway.
Personally in your position I think I would take a punt on a place like that (especially if BAME myself); I'm sure they exist in every London borough, but the two I'm thinking of here in Lambeth are Platanos and Lilian Bayliss. Possibly also Lambeth Academy, Evelyn Grace, St Gabriel's (know them less well). . . and Pimlico Academy (bit more 'upmarket' I believe so possibly one or two wmc's!) . . though like Holland Park not somewhere you can afford to buy, probably.
There's also Ashcroft in Putney - now that's super high achieving, super modern and well-resourced, but has v strict rep and is quite ruthless I've heard with kids who don't fit/strive sufficiently and may possibly have undiagnosed issues . . Bit of subtle offloading goes on, is the rumour. But it obviously does what it does very well, clearly appeals to ambitious immigrant families with traditional attitudes to discipline, and I'll be honest we were personally very tempted at the time.
Best of luck . . Personally I think London comps are fantastic in general, largely due to their brilliantly diverse intake and above-averagely wonderful, youthful, motivated staff. They are of course underfunded, and this is the biggest disadvantage especially for those with an impoverished intake; they can’t hit on the parent body for subsidies either directly or via private tutoring – and it is a worry.
I still think, though, the example of brilliant staff and students working miracles together in challenging circumstances is an exceptional life lesson for any child, from any background; easily worth a couple fewer GCSE options, or posh available extra-curriculars. Trust me, your child will be super busy anyway, and won’t miss them!