Ennara and the Book of Shadows by Angela Myron

Thirteen year-old Ennara Gaern expected studies at the Druidic Academy to be a breeze, and maybe studying magic with the world’s druid leaders just a little exciting. But when she and her friends are expelled from the school for beheading a prize dragon turtle and creating zombie flowers, her world is turned upside down.

When a theft of magical artifacts is connected to her suspicious accidents at school, she and her friends must find the objects before the Druidic Council finds them, and starts a war. And on top of everything else, Ennara must learn a new form of magic to stop her necromancy from destroying her world.