Make the speech therapist your best friend. This happened to my son several times but I reported this to the speech therapist who put those bullies in their place. Tell your son he is not alone and he will always have his mamma protecting him. Give him the confidence he needs to self advocate. Also please put your son in sports and martial arts to build his self esteem and confidence. My son is in high school now, a black belt, playing soccer for the last 10 years and a 4.0 student, and confidently tells people that he stutters. I know all his speech therapists and regularly talk to them. They know I don’t take anything related to my son’s speech lightly. You got this mom!