Your son's story is very much my own. At age 7, I moved countries. School. Culutre. Friends. The lot. Even lost my favourite childhood teddy bear in the move which was just extra trauma for little me. Before the move, I was very talkative. Centre of attention type of kid. After the move, I became very quiet and developed a stutter. At first, my new teacher claimed I was copying another kid in the class who had one. Her suggestion to my parents was to hit me every time I stuttered to stop me. Luckily, my parents aren't morons and totally dismissed the wild suggestion. Anyway, my stutter has varied in severity over the year. I'm now 34, and it's background noise now. I still carry it with me everywhere and have to adjust words and sounds to mask it, but it's manageable. My advice, instill your child with a ridiculous amount of confidence so the stuttering doesn't get to them.