We sent DS to Winchester. He left 8 years ago now, so very much under the old regime.
We chose the school because of the kudos that academic excellence is given, that being very good at Maths, or Music has a similar status to being in Lords (cricket) or in the first 11. It was a very good choice for us.
There are pros and cons to single sex schools.
Boys learn differently to girls - lessons can be catered to appeal to boys.
Mixed sex classes will add more breadth and a more rounded experience.
Boys do not have to conform so much to gender stereotypes and be so macho in a single sex environment.
Boys can learn to act in natural ways and work well with girls in a mixed environment.
The list goes on. In the end, as a percent you make a choice - DS always had/has plenty on friends that are girls, rather than girlfriends, so did not suffer from our choice.
There are plenty of all girls schools and so few all boys ones, which is why I’m centring the benefits to boys of this change. I will be a bit sad if they do change.