First question, what modern novel, set today, with the main character an American in a British boarding school, never even mentions Harry Potter? The Name of the Star by Maureen Johnson. No "I knew it wouldn't look like Hogwarts but...", no "when I put on my uniform, I grabbed a pencil, swished it at a pillow and said 'Wingardium Leviosa!'". Not a reference at all. This book definitely takes place after 2010 as it specifically mentions Amy Pond in her police woman kissogram outfit from Doctor Who. It is strange that I went along with the rest of the novel, believing that a girl who'd always lived in small town Louisiana would voluntarily move overseas for her senior year of high school, suspending my disbelief about how quickly she integrated into school, accepting ghosts as real beings who could interact with solid matter, but found it unbelievable that this American would not drop a hint about Harry Potter.
Anyway, it isn't a bad novel. Rory Deveaux moves to London for her senior year when her parents get jobs in England. She arrives right as a Jack the Ripper copycat begins murdering people, which does curtail her sightseeing. She begins to see ghosts, which she doesn't realize for a long while, and becomes embroiled in the Ripper investigation. It is a solid book, moves quickly, and has an interesting mystery. I would say a 5 as it is better than just tolerable.
FYI, book 2 comes out in about a month.