I'm atheist and he really needs to play that card a) because hes right anyway and b) as it's a Christian school it presents an extra opportunity for total pwnage with 'gluttony is a mortal sin. Stop allowing the sins or take your child elsewhere' - that being said Anglicans/Protties  arent real big on being told what's sinful in their homes by the pope cos that's the monarchs job while the Catholics would probably stfu at that stage.