BHS is about 8.45- 3.30 (DD in Y11)
She catches the bus from Burnham about 8am, and gets home on the school bus about 4.10pm.
There are after school clubs on offer - depends what your DD likes to do. But check she can still get home afterwards - for us, any afterschool activities entailed a parental car run for pickup (no public buses run North / South)
But even in Y7 my DD came home on the bus, walked home, unlocked the door and got on with her homework until the rest of us got home - no need for extended care (and she wouldn't have thanked me!!
In Y7 & 8 they had combined discos with various boys schools on various occasions. My DD has been involved with Scouts (Explorers) and Theatre groups outside of school to keep up some mixed gender experiences!