Shah was corrupt, to a massive level. He did some good, some of which came back to bite him. He educated many. I don't have knowledge of the split between middle and lower classes educations. But, consider this, education involves many options of how to manage/govern a people/nation. What happened was more and more people were aware that the Shah was indeed on the bad side of history.

Existing order educates the masses. Masses realize exactly how bad their situation is. Masses rebel, establishing a new order. In Iran, the referendum allow the religious fanatics to outnumber the reasonable (to myself) middle, to lower upper classes. Bingo, theocracy. Middle class loses all the gains they had under the previous order.