The new dumbness - the non thought of received ideas - is much more dangerous than simple ignorance, because it's really about thought control. In school, a washing away of the innate power of individual mind takes place, a 'cleansing' so comprehensive that original thinking becomes difficult. If you don't believe this development was part of the intentional design of schooling, you should read William Torrey Harris's The Philosophy of Education. Harris was the U.S. Commissioner of Education at the turn of the century and the man most influential in standardizing our schools. Listen to the man.
'Ninety-nine [students] out of a hundred,' writes Harris, 'are automata, careful to walk in prescribed paths, careful to follow the prescribed custom.' This is not all accident, Harris explains, but the 'result of substantial education, which, scientifically defined, is the subsumption of the individual.' Scientific education subsumes the individual until his or her behavior becomes robotic. Those are the thoughts of the most influential U.S. Commissioner of Education we've had so far."
Essay in its entirety: http://www.filmsforaction.org/news/the_tyranny_of_compulsory_schooling/