I remember reading that Head Girl was cut to ribbons by Armada! How exciting to have the whole one after years. I think it's one I didn't ever read as a child, so I've only ever known the full version. It's not an absolute favourite of mine, but I do like it very much - it's a gratifyingly chunky one, isn't it? Also I am really rather fond of Grizel, as a child and an adult, so I like the focus being on her.
New Beginnings goes up in my estimation simply through knowing that the author agrees on the cover art.
I shall keep an eye out for it, if I can pick it up v cheaply I will give it a go. I'm afraid I can't think of anything that quite fits the bill on the SDL... that may be because I almost exclusively read the slash
I love New for how slashy it is.
Especially the bit where Nell is all "no no no, we'll stick to my plan please ". But it's also the one with the lovely bit where they go running through the school hand in hand after the first staff meeting of the term, and there's also something pleasingly slashy about the night on the coach (rather ruined by the presence of Joey, but nonetheless there is something about it. There's also a super-short piece on the SDL inspired by that, so it's clearly not only twisted old me who loves it!)
Actually, related, I am always interested in recommendations of similar books with slashiness in them. I picked up Gladys Mitchell's Convent on Styx initially because of a brief moment where a minor character references her own lesbian appearance. And also Lady of Letters (Josephine Elder, much recommended) because the main relationship in it (between the female protagonist and a spinster colleague) is so compelling. I am eagerly awaiting delivery of one of the Upson books on Josephine Tey, which is apparently suitably queered. 