Hi! SLP here. It sounds like your last SLP was more focused on fluency techniques and less on confidence in communication - fluency techniques are only helpful because they're novel, if they are used all of the time, they work less effectively. Though they were correct about needing your son's buy in for therapy to be effective. Try finding an SLP on your area who can help him learn that stuttering is okay, ways to disclose his stutter to others/feel more comfortable when stuttering happens, and how to get involved with the stuttering community. In my area (Portland, OR), there are support groups and summer camps for kids and teens who stutter. I think that's one of the best ways to support teens, especially. Also, I don't know if you watch Survivor, but I've been recommending the current season (48) to my clients who stutter - there's a castaway who stutters this season, and he does some great work advocating for himself!