Actually your IQ does decrease in old age, but usually not much.
I highly distrust online IQ tests, as results can vary wildly. I've scored as high as 182, but realistically I'm probably in the 140s. About a year ago they had that "America's IQ" show on, and I think I missed one question, but the top of their scale was only about 135 (I guess a show's no good if it makes people feel stupid.)
TippmannNut has the dubious distinction of being the only person I've seen score less than above average on an uncontrolled test.
School grades don't necessarily show intelligence either, I found school boring early on and slacked like hell to graduate with a 2.6 GPA (even got a D in Honors English, because I hated writing essays!!).
