Doesn't seem like a believable motivation to me. You don't need to literally light things on fire to tell when forest conditions are like a tinderbox, let alone do it 14 times. I figure this guy knew in his gut that the government was setting those fires, and if he could just find some evidence then he could crack the whole case open and people would stop calling him crazy. Of course he can't find any such evidence (because it doesn't exist) but he knows in his heart what's happening so what's the harm with creating some 'evidence' to move things along?

Stay-at-school suspension for 4 years.

He could not test that by collecting some samples and using a fireplace?

Yes. But only if they refuse to acknowledge that you're an adult and don't belong there. Otherwise it's just reading small books and adding numbers together manually.

Billy Madison style