The first book has a scene where the student almost dies due to a werewolf-like creature and is saved and recruited to a magic school. The school has a sanctuary for animals. The cooks at the school are Bob the troll and a hag who tries to eat the students on occasion. The main character learns how to the fight the werewolf-like creatures. The students play soccer on a magic field that changes (hills are added to the field during play). In one scene, the main character is in an art gallery and is almost killed, and the school is under attack in the last book of the series
Pre- or post-Harry-Potter? If pre-Harry-Potter, you could try Groosham Grange, 1988, School of Wizardry, 1990, and Wizard Hall, 1991.
I think you’re describing the Tapestry series by Henry H. Neff, first book is Hound of Rowan. It does have Bob the Ogre and the hag.
https://www.supersummary.com/the-hound-of-rowan/summary/
https://en.wikipedia.org/wiki/Henry_H._Neff#:~:text=Neff%20is%20the%20author%20and,format%20on%20November%2025%2C%202014.