Well if you know each other then why don't you tell him before or after school, when you're alone? And, for some reason, boys mostly tend to like going out with girls who are younger than them. Of course there's some who like older women but that's besides the point.
Well do you know him? Like talk to him and stuff? And he might not think that. I'm pretty sure that it's not [i]that[/i] bad for someone to go out with someone a year younger than them - plenty of sixth form go out with girls in my year and the year below me.
I mean... DALEK. WHAT EVEN.
Gah.