Both Darrick Wood and Langley Boys have very good reputations, but you will need to choose one or the other when it comes to buying a house as you are not likely to be close enough to both to be sure of a place. As with all senior schools, look at GCSE results, rather than A levels, as lots of people change for 6th form, and all schools are selective at 6th form, to a degree.
Langley Boys now have an amazing concert hall, and a very good music department.
We lived fairly close to Darrick Wood for about half a year, a few years ago, (we would have been close enough for a place, if we hadn't been moving away again) and it is a nice area to live. If you were living near there, you would also be close to St Olaves, if you wanted to look at it. It is super selective, though, so not everyone's cup of tea. (I assume you have boys, as you mentioned Langley Boys and not Langley girls!)
We rented a 3/4 bedroom house not far from Darrick Wood, with woods at the end of the road, and fairly close to Orpington, Petts Wood and Locks Bottom shops and rail stations. I think you would pay around 600k for similar.
I think Bromley is pretty much as ethnically diverse as most outer London suburbs. You would be unlikely to not have a community of "your" people, close by, as it were, but equally, like the rest of London, people of all ethnicities tend to mix and be friends.