SOLVED. YA mystery — has brilliant illustrations in a scrawly style, about a young girl (who has a pet dog?) at a (monster?) school. [s]

[carmen]

I must have read it when I was 9 or 10 I reckon, so year 2012/13 ish. Can't really remember the plot, I remember it being a series however.

Random details I remember: the butler is a frankenstein type, they play croquet on horses who have large fringes, one of her friends is an invisible boy who wears glasses, there are a lot of secret passages in the school

[Kris]

Carmen, can you tell us something about the mystery?

What about the girl (e.g., her age, special powers, favorite subjects, hobbies, personality)?

[carmen]

she likes solving mysteries i believe. i think she’s 15 y/o ish, her dog likes to follow people around so she finds a few clues that way (secret passages etc.) she also has a whole hallway of paintings of famous people at the school i believe... sorry this is so vague!

[Pheiffer]

Is it Ottoline goes to School by Chris Riddell?
Ottoline Goes to School

[carmen]

Pheiffer wrote: "Is it Ottoline goes to School by Chris Riddell?
Ottoline Goes to School"

yes it is!!! you are magical thank you :)

[Pheiffer]

You're welcome! Riddell is one of my favourite illustrators ever :)