SOLVED. Fantasy Children's book/series about a boy who joins a school that's set in an underground cave. [s]

[Gwen]

I read it around 2015 it might have been a little later. I don't remember to much and I'm not sure all the information is correct.
I don't remember much but one of the villains hade a mask on and the fact that he had a mask on was important and focused on a lot.Before the mc joined the school he had to do a test with a lot of other children to see if he had magic and during that test he exploded a pen with his magic. During the school year they had to solve a puzzle/do a test and that required him to travel along the rivers with a boat in the cave. The main character gets a dog or wolf. I think the dog is a magical creature. Also his father turned out to be evil I think and the main character discovered that by looking through his father's basement and it also had something to do with the dog. The mc ran away. Mc and his friend also went on adventures where they had to change there clothes because where ruined and they had fight something while visiting someone's house. Also it the mc was the chosen one? And there was this big final battle/war.

[Becca]

The Magesterium series by Holly Black? The first book is The Iron Trial.

[Gwen]

yes it think that's it. thank you so much!