This song will use an open A chord, and then a variation. For this variation, you lift your pointer finger off of the string and play the rest of the chord. Easy enough. I'll refer to the variation as "Av"

You use:

A, A, Av, Av As the intro, and for the whole first verse.

The pre chorus is:
Bb                   E
But, just a little different ooh...

Then the chorus:
A,     Av, Bb,    E           A, Av,
Special Ed, Momma dropped him, on his head,
Bb,      E,      A,       Av,   Bb,     E,         A, Av.....
Now he's not so bright, instead, he's a little bit special...

Then it goes back to the verse format. There's a part in between where he talks about ed hitting him with a brick... use bar chords and figure it out yourself :) Then it goes back to normal more or less.