"Paper Covers Rock" by Jenny Hubbard

Thomas, Glenn and Alex went to the river to relax, and escape some of the stress of their elite boarding school. Someone had a bottle of vodka, and all of them were drinking more than they should Someone bet Thomas to jump off the big rock. Glenn and Alex jumped, but when Thomas did, he didn't have enough clearance. What was supposed to be an afternoon of leisure, turned into one of horror, as Glenn and Alex realize their implication in their friend's untimely death. And they make a pact to not mention alcohol to school officials, in order to cover their tracks. But Alex is not dealing with his grief well. He starts a secret diary, which he keeps hidden in the school library. And his English teacher, Miss Dovecott, suspects he may not be sharing all he knows about the accident. Glenn and Alex devise a plot to get Miss Dovecott fired, and out of their business.