The Marvellers by Dhonielle Clayton
Eleven-year-old Ella is the first Conjuror to attend the Arcanum Training Institute, a magic school in the clouds where Marvellers from around the world practice their cultural arts, like brewing Indian spice elixirs and bartering with pesky Irish pixies. Despite her excitement, Ella discovers that being the first isn't easy, and not all Marvellers are welcoming of Conjurors. But eventually, she finds friendly faces in potions teacher, Masterji Thakur, and fellow misfits Brigit and Jason.
When a dangerous criminal known as the Ace of Anarchy escapes prison, supposedly with a Conjurors's aid, Ella becomes the target of suspicion. Worse, Masterji Thakur never returns from a research trip. With her friend's help, Ella must clear her family's name and track down her mentor before it's too late.