The Academy by Elin Hilderbrand and her daughter, Shelby Cunningham

 The Academy tells the story of a boarding school in New England. A wealthy benefactor is keeping it afloat and the benefactor's son is flouting all the rules. As the story starts, students and faculty are still recovering from the suicide of a popular student the previous spring. The school has 2 new teachers and a new student who dresses like she's stepped out of the pages of the Preppy Handbook. All of which is causing a fair amount of turmoil. Then someone lets loose a new app called Zip Zap, which manages to uncover a lot of long-held secrets.

I read it all the way to the end to find out who had unleashed Zip Zap (and I guessed right). But this is not my favorite book by Elin Hilderbrand.