Hello and thank you for using JustAnswer/Pearl for your question.
Is this of recent onset or has this been a life long problem?
There are neurogenic (physical) causes of stuttering, as well as psychogenic causes. Treatment depends in part on determining whether or not there is a physical problem. If for example, the stuttering was of new onset, then it would be important for your son to see a doctor soon, since there could be a neurogenic cause of the stuttering, and if that was the case medical treatment may be needed. For example a mini stroke, or even a tumor can results in stuttering depending on the part of the brain effected.
Ideally, after having any physical problems ruled out by an MD an evaluation by a Speech Language Pathologist would be done to assist in determining the best treatment plan.
Treatment for teens and adults with psychogenic stuttering may includes individual assistance for a speech pathologist or speech therapist who may instruct on
"learning ways to minimize stuttering when they speak, such as by speaking more slowly, regulating their breathing, or gradually progressing from single-syllable responses to longer words and more complex sentences. Most of these therapies also help address the anxiety a person who stutters may feel in certain speaking situations." (Reference: MedicineNet, see this LINK
Along with individual therapy, support groups with others having similar speech problems are often effective for adults facing the challenges of stuttering.
To find the professionals and resources that are available in your area (lists of doctors and other clinicians who diagnose and treat stuttering) go to the National Institute on Deafness and Other Communication Disorders (NIDCD) website, by double clicking HERE
I hope this is helpful but please do reply with any questions you may still have, or if you need assistance with the NIDCD website.
Please follow up and let us know what proves helpful for your son.