I haven’t read the first one, which now I really want to do.
But even though I haven’t, I was able to read this without feeling I was missing half the story. This can easily be read as a stand alone.

It reminded me of the Private and Privileged books by Kate Brian: set at a school, full of mystery, suspense, murder and a plot that makes you think you know who did it, and then throws you for a loop.

Brilliantly written, superb read.