Be kind to him and supportive, speech therapies also contains behaviour of parents towards the child, it is critical. Parents and child both have to do hard worl over here, it is your duty that your child will do the exercises and techniques, be supportive, understand his point of view and guide him. Do not listen to others who are saying speech therapies are useless, I know many people who went through speech therapies in their childhood and manage to cure stuttering, because in childhood neurons are still forming.