In the end the reason why this was the correct thing to do is that if he had come one day with a gun and started shooting people the school would be blamed for not realizing that something was going on. School shootings are very serious and the school staff should be proud of properly preventing it.
What a ridiculous and extreme response to a kid having a little fun. Total nonsense. He was engaging in satire of our advertising inundated culture. And it's his parents responsibility, not the schools, to discipline him, if any was necessary. Total breach of both parental and individual rights. (Assuming the young person is under 18 and living at home) I guess they're just being typically Canadian, North America's socialist nightmare.