Is Advertising in Schools an Empirical Prediction?

In your book, you talk about allowing advertising in schools. You say that this degrades our sense of school as his important and sacred place. But i'm still wondering whether, a, the change in norms is an empirical prediction or if it's almost by definition to you that this change happens. Would you consider just the act of having advertising in schools to be itself a bad thing? I think it would be worth asking what is to on term effect on norms?