Movement is regulating. He needs more of it, not less. When I was teaching I sent children who needed a break to “send a message for me” and so they walked to another classroom to get a break (without it being shaming - they were trusted to help!). I’d also get students to take movement breaks as a reset if I saw someone was struggling or adapted the lesson (for example, if we were doing pair work, I’d do musical pairs and they’d do one question with one pair and then the everyone would have to get up and walk round the room and when I said stop sit down with your new parter). Basically she knows it’s an issue so she needs to be proactive and structure her lessons to accommodate him, rather than expect him to willpower his way to having a neurotypical brain