Hey, I thought this site was open to Canadian users as well. 
Speaking as one - whether you should be concerned about a possible drug charge is essentially up to your parents.
Whether you should be concerned about a possible arson charge is up to the school. I gather they haven't filed a complaint yet, so I don't know what you're worried about. As stated previously, we can't read minds. In the event they DO file a complaint, you might be charged with arson, damage to property (s.434 of the Criminal Code). You might also be charged with ancillary offences like possession of incendiary material. It sounds like you are guilty. It also sounds like the offence (burning a book) was very minor in nature and I would expect you'd get little more than a slap on the wrist (suspended sentence, conditional discharge, something like that).
I don't see why you would need to speak to someone versed in both US and Canadian law. What you should really do is speak to a local criminal defense lawyer.

Speaking as one - whether you should be concerned about a possible drug charge is essentially up to your parents.
Whether you should be concerned about a possible arson charge is up to the school. I gather they haven't filed a complaint yet, so I don't know what you're worried about. As stated previously, we can't read minds. In the event they DO file a complaint, you might be charged with arson, damage to property (s.434 of the Criminal Code). You might also be charged with ancillary offences like possession of incendiary material. It sounds like you are guilty. It also sounds like the offence (burning a book) was very minor in nature and I would expect you'd get little more than a slap on the wrist (suspended sentence, conditional discharge, something like that).
I don't see why you would need to speak to someone versed in both US and Canadian law. What you should really do is speak to a local criminal defense lawyer.