Off the top of my head, I think Ivy Norman moved there? I think
she's the one who was originally Head of the Kindergarten they started there, and the assumption is that she stayed on when the school joined them, although Dollie Edwards became Head of the whole school. (Which would obviously have been fine with Ivy! She'd've hated having to come the Headmistress over the Middles and Seniors
I'll have a glance through my books and the encyclopaedia when I go upstairs and see if I can come up with anything more helpful.