how old is kearney?

it's been well established that he has a son. and a reference that he remembers how great the bicentennial was,yet he's still in elementary school. so how old exactly is this charachter. maybe they've given a clearer idea in simpsons comics? at least give some more references from episodes that give clues into kearney's age if you think of them.

I'd say 25-26.