Nothing amazes me about what "Cahtolic" schools or churches do anymore.
This is a Catholic School and Catholic Schools are known for their strict rules and dicipline. That's why many parent send their kids to Catholic School. We want our kids to understand the importance of the rule of law in a civilized society and the consequences for breaking those rules. We want our kids to learn in a safe enviroment without the disruptive influences and distractions of a few attention whores.
I'm willing to bet that he was denied the diploma not because he Tebowed, rather, he failed to follow the graduation protocal. If the school had let him get away with this, then next year another attention whore will distrupt some school event in the hopes of topping this guy, and the cycle will contine and expand.