Sorry to intrude on Kent but I'd like to know if you are talking about a raw score of 90%. I am so curious as to where these figures come from. Do your LEAs publish these figures for general consumption. Where I live in North London all the schools have different entrance exams. Some have VR/NVR/English and Maths NFER MC, others have in house published written papers, others have a combination of both. However, no school lets on what sort of score one should be aiming for to even be in with a chance. Its just the top 180 or 160 or 64 or 24 depending upon which school you are looking at. The score needed to achieve a place will obviously vary depending upon the strength of the cohort. Lots of people on this website quote statistics ie 90%, 85%, 70% etc but its always nice to know the source of your statistics where possible ie fact or anecdotal.
In Kent the 11+ is set by the LEA, not the individual Grammar schools, so you only have to sit one 11+ (which consists of four papers in VR/NVR/MATHS Nfer MC, and a written English piece, only taken into account for borerline fails)and you can apply to any grammar school in Kent.