The Cavendish Home for Boys and Girls by Claire Legrand

At the Cavendish Home for Boys and Girls, you will definitely learn your lesson. An atmospheric, heartfelt, and delightfully spooky novel for fans of Coraline, Splendors and Glooms, and The Mysterious Benedict Society.
Victoria hates nonsense. There is no need for it when your life is perfect. The only smudge on her pristine life is her best friend Lawrence. He is a disaster-lazy and dreamy, shirt always untucked, obsessed with his silly piano. Victoria often wonders why she ever bothered being his friend. (Lawrence does, too.)

But then Lawrence goes missing. And he's not the only one. Victoria soon discovers that The Cavendish Home for Boys and Girls is not what it appears to be. Kids go in but come out...different. Or they don't come out at all.

If anyone can sort this out, it's Victoria-even if it means getting a little messy.