Is there anyone in the school competent enough to go into the classroom and observe his behavior, like a school psych? You could try asking for a functional behavior assessment. http://www.wrightslaw.com/info/discipl.fab.starin.htm
If someone goes in and watches him, they they can see for themselves what is triggering behaviors and you'd have a better idea of what to put in a 504 plan. Of course, if no one in the school is competent enough to do this (which would be the case in our school), it's pretty useless.