Need context here. How severe I Is the stutter? Is it accompanied by anything else other than the jaw movements (twitches in the face, muscle tension)? Did he used to stutter when he was younger? Most cases of stuttering begin early on in childhood, so a case of stutter solely beginning when someone is practically an adult can point to a traumatic event (brain injury or PTSD). The doctor can also do so much too, but it's worth giving them a visit. However, speech therapy outside of school can be very costly (it's $100 per visit in my state). If it comes to the point that your child needs therapy, go with a school therapist if possible. We're always here to help, so ask if you need help!