Matt is not above zoning out during class. Most of high school involves wasting his time, one way or another. Science, history, none of that means much against the Swiss cheese that is Matt's life. Nothing quite fits together- there's too many holes. He still has panic attacks every week. His parents still don't believe him. He can't talk to girls without choking on his whole personality, which stays safely hidden under a layer of pretty little lies.
It's really not a big deal to zone out during class, because the chances that he makes it through high school without turning a gun on someone are slim to none. Matt is more Macbeth, with his wife whispering in his ear, or Hamlet, with his father whispering in his. So he's going to doodle; maybe then, his teenage angst won't have a body count.