Had the cloaks in my day as well Neolara, and scratchy Harris tweed skirts.
I agree about the emphasis on being kind. It seems to be something that has stayed with my peers, with several working for charities or in public sector jobs like teaching or medicine. I also agree about the academics.
Academics do seem to have changed. Mayfield does well for a non selective school, particularly in STEM subjects. My understanding however is that they are working hard to retain their ethos, seeing an increased demand for boarding, partly from London families who are seeking something gentler, and more nurturing. Singing (Mr Pont is apparently still around), pottery, riding and more are still strong, so, unlike some other schools it is OK to be clever, but equally OK if academics are not your thing.
One of the advantages Catholic schools have is that overseas boarders tend to come from Catholic communities, so you get a good mix: Poland; Mexico; Nigeria; East Asia, which helps with integration.
In terms of numbers who stay weekend you might ask the school and what they do. You might also ask about how boarders and day pupils interact at weekends. There is a MN orthodoxy that full boarding is essential. Yet DD's experience of being a sixth form day pupil at a school with boarders was that she often went in at weekends to do homework with friends, and then out for supper after, and that boarders would occasionally come and stay with us (with housemasters permission!) at weekends or for half term. She often had matches on Saturday as well.