I agree with Emland. Where I live, which is in Rock Island, IL, there is a possible fine if someone who is required to attend school does not do so.
If he were my son, and the problem turned out to be solely because of his attitude, I would find out what the possible fine would be by going to the courthouse or asking a truancy officer, and then show documentation concerning that to my son.
Just to give you an idea about fines and the way that things proceed in situations like this, the following sites may be of use to you:
www.jp.hctx.net/truancy/Truancy.pdf
School attendance: your responsibilities - ParentsCentre
Information about Failure to Attend School Cases