Gross or over reacting?

So, it's not about sex, but this guy I've started casually seeing (we haven't hung out outside of school yet) he's turning 16 at the end of March and I'm currently 17, he's only a year and a half younger than me but I'm a senior and he's a freshman. He's supposed to be a sophomore and I'm supposed to be a junior. People keep telling me this is weird and gross and I'm a cradle robber. Is it really that gross? It's only a year and a half and we aren't together for sex.