Looking at some of the league tables for non-grammar school options is leaving me decidedly unsettled about those schools, but I need to make sure of provisions in case he doesn't pass the 11+, so am aiming to include 3-4 schools which aren't grammars.
Regarding League Tables, remember that the academic cream has been taken off the top for Upper schools so you really need to look beneath the superficial league table result that the papers publish. To properly compare the upper schools I would look at the Performance Tables on the Department for Education website http://www.education.gov.uk/schools/performance/
I would look at the proportion of high and middle achievers within the cohort and also the proportion of those high and middle achievers making expected levels of progress. If you think your child is borderline grammar school material then they would probably be classed as a 'high attainer'.
I wonder if the proportion of 'high attainers' in a cohort could also affect timetabling options for GCSE (adversely if there are very few wanting to take traditionally academic subjects).
For example, look at the difference between Chalfonts Community College http://www.education.gov.uk/cgi-bin/schools/performance/school.pl?urn=110529
with 23% 'high attainers' and the Cressex Community College http://www.education.gov.uk/cgi-bin/schools/performance/school.pl?urn=110500
with only 6% 'high attainers'. Note that schools that have recently become an Acadamy are treated like a new school and you have to look at their historic results (under the non-academy name).
PS. I am not suggesting that Chalfonts is a Wycombe school, I just picked it for a comparison