I agree with the earlier poster. Having been through the 11+ 3 times over the last 6 years, including having a son a Kegs, consensus is that 85% or above gets you into Kegs and 82/83%+ into County High. This number does not equate to the the score the consortium give you, such as 371 but is a rough guide taken from the raw scores that your child achived in each of the papers. So for instance,
The percentage is calulcated as the sum of:
Maths (30/40) * 0.25
English (30/40) * 0.25
VR (67/90) * 0.50
The Consortium use some complex Maths to calculate a "normalised" score for your child but say you took your childs raw scores and worked out the percentage he or she achived in each paper and then an average overall, remembering to give VR a 50% weighting and Maths and English only 25% and the mark came out as 75%, the "normalised" score you get from the consortoim will be very close to 300 out of a possible 400.
It is harder to get into the Royal Grammar School becuase becuase there are only 96 places as opposed to 112 at Kegs. I believe that it's generally agreed that in terms of academic performance at GCSE, there is nothing between the schools. Do be aware that the Royal Grammar in Colchester does perform better at A level but this is in part achieved by "culling" a large number of boys after the GSCEs and offering their places up for competion, particularly to overseas pupils. If your child comes very high up the order of merit in the 11+ for Colchester, you shouldn't have anything to worry about. On the other hand, if you expect hem to get in but finish in the lower quartile of entrants, I'd be concerend.
Not sure I agree with the last comment. I know children that have got into the grammars just (i.e. maybe in the last 10 positions) and they went on to be very successful. What we have to remember here is that a lot of children a tutored purely for the 11+ - yes, they have to be relatively bright to get through but it doesn't mean that if they come high in position in the 11+ they will be in the same position in the school. I know one girl that got in on appeal and ended up being 4th in the year at the end of year exams and I am sure she is not an exceptional case. There are many more subjects for the children to cope with than what is tutored for the 11+.