Hi Maria, I can't comment on the particular schools you mentioned as I am in N.Bucks, but to generalise, schools in Bucks do not actively encourage or get involved with the 11+.
Obviously all primary schools in Bucks have to familiarise their pupils with the question types over a period of 5 lessons during June/July time and occassionally heads really get involved in the familiarisation papers and diligently work through them with their pupils, however, others merely read through the question booklet and go through the motions - pot luck really.
But whether we like it or not, however, enthusiastic a head/school might or might not be, a child will only get through the Bucks 11+ if they undergo tutoring with a dedicated 11+ tutor or have parents/family help (DIY) via this site or similar.
Schools, in theory, have no knowledge which pupils are preparing for the 11+ and what method they are using.
As you probably know, for many children, the question types are not that hard to master, but the children need practice to complete 80 of them in 50 mins, no mean feat at 10 (or at any age!!) and this is what needs the practice, exam technique more than anything.
I think you need to ask around. It's hard because 11+ is quite often a taboo word, tutors names are guarded secrets and parents will quite often say 'my child wasn't tutored' - they don't count helping at home with practice tests etc, vocab etc. as preparation!!! It's a bit of a minefield and I don't think you should look for a school with your main priority being 11+ passes.
My advice would be to look for a school with enthusiastic and bright teachers, happy children, bright buildings with outdoor space, school trips and of course good SATS results and then ask (some won't tell) how many children are successful at 11+ to see if you can join a like-minded local ' 11+ gang'
You also need to think about what grammar school you would like your children to attend if they get lucky and ensure you are in the right catchment area and also if they are not lucky, what will be Plan B and are those schools appropriate.....
I am sure someone will come by soon with comments on the particular schools you mention, so good luck.