Consult a therapist before making a decision

My son is into marijuana and he does not do well at school. He has an attitude problem at home and I do not know how to make him understand that he is putting his future at risk. He is a very bright boy who seems determined to throw his future away. I am threatening to send him to military school. He doesn’t think I will do it but I might. Do military academies work well for kids who aren’t doing well in regular school and are doing drugs and getting into trouble. It is very hard to get a straight answer from anyone about if they actually work or not? He would hate it there and I would miss him but I am worried that unless I can get him back on the right path now while he is only 13 then I will miss my chance forever.