I passed, and went to a mixed grammar school.
22 years later, my own daughter didn’t pass. I was disappointed, particularly as a few boys, who had not seemed as bright, did pass.
The very wise headmaster at the primary school pointed out that boys were often late developers, compared to the girls, and how they seemed at 11 didn’t necessarily equate to their ability at 14/15. So if boys didn’t have to attain the same pass mark, perhaps that is why.
My own GS and GD now attend the same grammar school as I, and their father, attended. It’s a good school and attracts children from a wide area. A certain pass mark has to be attained, if over-subscribed, then those living closest to school get a place.