The Iron Trial: Book One of The Magisterium

Iron Trial  is another spin on the Harry Potter school of fantasy. An outcast boy ends up at a magic school and bonds with another boy and a girl. It turns out they have some key powers that make them key in preventing a great collapse. They need to gradually learn their role.

Most everybody would love to pass for the "rewards" it entails. Callum Hunt has been told by his dad to stay away from magic, making him one of the rare people that want to fail the trial. Alas, a mage brings him in. He seems to have unbridled power. They want to help him control it. He can interact with other beings such as a "pet" he has. He is told that he may be much more than he thinks he is. 

The book ends with a "resolution" to a minor episode. It is pretty clear that there is much more to come in the future books.