Tell your mom to piss off if she insists on pushing religion, and if complications around the dinner table continue, suggest that prayer be done silently.
As for the Christian school, teach your son a nice little sentence like:
"My beliefs are not yours to mold. If I want to hear about Jesus, I will ask."
Seriously, I would get my kid to do this.
Which is probably a reason why I am not going to have children.
