My child can't take part in whole-class activities like morning meeting or lessons.

Morning meeting and whole-class lessons pile up demands—sitting and listening for a long time, understanding whole-group instructions, switching. "Can't take part" doesn't mean "no motivation." Discuss accommodations with the teacher: seating, a visual schedule, breaking activities into short segments, giving a role, a place to calm down when it's hard. Rather than insisting on the same form for everything, treat "watching-participation" and "partial participation" as participation, and widen it gradually.