Hi TandC.
I live in Farnham used to live in Ashtead and my sister lives in Bookham! So I have some perspective.
The state secondaries in Farnham are good as they are all above national average in results but they only go to 16 - the children move to sixth form colleges and the two best are Farnborough and Alton - both with really great national level profiles, I believe.
As mummytime says, Frensham heights is the only independent secondary in Farnham but it is alternative. I've known lots of happy children there, but it wouldn't have suited us.
My own kids all went to the independent schools in Guildford - there are boys and girls schools in the national top 10 academically. Other great alternatives exist locally and there are buses to Lord Wandsworth, st Nicholas, Salesian, Farnborough hill and more. There are lots of options and something for everyone.
But I've said it before on here - if you have a choice, and are planning on sending your kids to the Guildford schools, for their sake, live on the up train line from Guidlford. Direct trains from east Horsley and Claygate take a fraction of the time that the Farnham travel options take ( 2 changes for the girls). That said, mine have always loved the train travel.
The Howard at Effingham is also a great school but you have to be careful where you live - there was a big brouhaha a couple of years back as whole villages lost out on places, so you'd want to check that out if that was your chosen school.
Other schools accessible from Ashtead, say, would be Thursfield at Leatherhead, where I've known very happy friends' children or St Andrews. And private options include Freeman's at Ashtead, Epsom College, or St Johns. All of those also easily reached from Bookham.
So lots of great school options from any of those places. So I think it'll depend on what kind of town you want to live in - Ashtead to me now feels like outer London - not necessarily a bad thing - good access to London is important to me too. Bookham has more fields. And there are even more green spaces by the time you get to Farnham. And Farnham is not too far out at all - I drive to London every Saturday and it takes exactly one hour to Kensington door to door. And I drove to Leatherhead today and that takes about 40 minutes.
So let us know what you decide and any specific questions, bat them this way!