I don't know what to say, except giving my sympathies and support here.
It strikes me that Mo is inclined now to miss school, perhaps there is the key
to everything - kids at school can be so cruel. You might not get anything
out of Mo, but perhaps other kids around him.
That's always my take on things, I ask several kids what's going on, and usually
can put two and two together.
Good luck in getting this resolved!