Updating ios systems on the ipad's, automatically set a passcode to access the home screen. You can imagine the dilemma when the children thought they all knew what the code was when ipads were handed out with passcode still in place. It's really simple to reset even if you get to the stage of the ipad being completely disabled. YES we got that bad.
Follow these steps and problem disappears. You will need to upload purchased apps from itunes again but doesn't take long.
The magic link!!! http://support.apple.com/kb/HT1808