Why do people always ask my race and then look at me funny when I answer?

I'm puerto rican and sicilian. I'm kind of "different" looking. I get called exotic looking so I guess I understand why people always ask me my race. Even my teachers have stopped me in the middle of class to ask me my race (which I'm not even sure if that's legal lol). And then when I tell them my race they stare at me. Sometimes they mutter "weird" under their breath. I mean, is it THAT weird? I don't get it...