Per student spending higher than stated

The cost per student figure is an oft used tool for both sides of school issues.
Now we find that the costs may be higher than stated and that should open up a big can-o-worms.
So, why would they hide the actual costs?
They don't want us to know how much money they are wasting when they continue to say we aren't paying enough.
They also don't want us asking hard questions about how so much money translates into unacceptable results.