Sorry just seen this thread. I understand what bombardier is saying but that is what I think of as typical NGHS arrogance!
I had family children go through NGHS and the High school and spent a short time working at Trent College.
In my opinion the schools are just different rather than better or worse. If your child is bright they will maximise their ability whichever of the private schools you choose.
The high school (formally boys now mixed) is seen as a hot house for academic children, quite pressured and does get good results. NGHS has really focused on the girls only angle as this is what sets them apart, I am not keen on it at secondary myself but that’s my personal opinion, not sure it’s an issue at primary level.
The Elms (Trent college) doesn’t have real testing for children coming in at this age although they will want to ensure she would fit in and be the right school for her. Later on in the school life there is testing to continue to trent but it isn’t as academically selective.
It’s hard to compare private schools without knowing what you want and what your child is like, elms is a more rounded education and they excel at sport, music, drama as well as academia. This means days can be quite long and might not suit all. They also currently have Saturday school from (I think) year 9 onwards.
I think visiting all the schools is important and deciding on what’s most important to you and your child.