Aside from the fact that SpongeBob can start a fire, visit the beach, blow bubbles, and play in the snow -- all while living underwater, I have trouble figuring out exactly how old he is.
How old would someone be that:
* Goes to school (teacher is Ms. Puffer)
* Works a job (Krusty Krab)
* Lives on his own (not counting his pet Gary)
So is he a kid that has no parental supervision and not subject to child labor laws? A teen? A grown-up who never graduated from elementary school?
Moral of Story: Kids -- stay in school unless you want to flip burgers and live in a pineapple with no one to keep you company except a snail.