@Ju2020 - In case useful, in my humble opinion, there is no 'best school' in absolute terms, but schools more (or less) suitable for different children. Visit the school (if possible, in these Covid times), speak with teachers, head and children, and with families with recent direct experience, and get a feeling for the place, the ethos and the families. At the end of the day, you know your child better than anyone else and you also where him/her and your family would feel more comfortable. We visited schools considered as "highly desirable" and strongly felt that their 'factory-like' approach to education did not work for us and were lucky to find one, in Roche, that we considered was more suitable without having to compromise at all on the academic front. I am delighted with the decision taken and I am happy to share my insights, but will always steer clear of advocating that I am in the right and others in the wrong.
As for school results, they are usually available on the schools' websites and I am sure you will peruse... I think that they speak for themselves, but it is always useful to refer to offers received and places accepted (not only accepted one), and to do so in the context of whether the school is selective or not. Useful also to look 3-4 years. Similarly to above, I find reassuring that Roche has got children into St Paul's Girls and other top-academic schools, but also know that children able to get into such 'aspirational' schools have, in the past, opted for others that fit their personality and interests better.
Good luck with your search and choice. I gather that you are in SW London and we are lucky to have many lovely schools in the area - to add to the reference to Hurlingham (which we did look into and is indeed popular in the area), and following with the co-ed theme, you may also want to look into Prospect House and Finton House (no personal experience of either, but I know families with happy children in both schools).