Take a walk through your schools and check out how many of the doors are chained shut. School security drives the fire code inspectors crazy - should get parents upset too.
WD40 is a solvent. It dissolves rust, etc., to free hinges, etc. Then you have to wait for it to dry or wipe it off and apply a proper lubricant. Unless you use it for bike brake pads or other odd uses. And wow I'm pedantic late at night... *blink blink*