What Does It Mean When A Boy Pretends Not to Notice You?

I have a secret crush on a boy I have never met before, but have seen around. Everyone waves to everyone here, so I wave to be friendly. But when I acknowledge his existence, he pretends not to notice and just look down or away. I know he has noticed me before. What does it mean? Usually people here are friendly when you wave to them. Even his younger brother is really nice to me, but he just pretends I'm not there. I don't know if I should even like him anymore. I've been starting to ignore him. What's his deal?