What do you do when a guy likes you at age eleven?
Invite him for a cinema some of these days, and kiss him tenderly. He will never forget. Do this good action. Then keep on talking and say that you love him too, when both you arrived at "his" home. Kiss him again and say : good night, sweetheart.
If you mean eleven years of age , which I presume you do, just be outright with it. Get him when he's on his own and ask him , " Do you like me?" (maybe say that someone else ie. a friend says that she thought you the guy like you). Or you could post a note in his locker, ask him through a friend or ring him.