Monster Match (Frankinschool #1) by Caryn Rivadeneira
Fred is working diligently on his writing assignment when a mist fills the room, and the words on his page come to life, literally. Suddenly Fred―now Frankinschool―and Luisa―now Princess Luisa―need to save the school from the mysterious potion―and the even more mysterious and devious ghost living in the school attic.-Goodreads