You don't say whether your son is on medication for his ADHD. If he is and he's still having such difficulties with concentration, impulsiveness, etc., it sounds like the medication may not be monitored adequately.
Has any direct intervention been prescribed for his difficulties in class? For example, social-skills training classes or a behavior-modification program with very specific goals and charting of progress? These interventions do not have to take place within a special-education class -- but they certainly can.