All teenagers think that their parents are stupid. Then when they become adults they come to this realization that their parents, while human, are actually pretty wise people after all. Having witnessed (and experienced) this particular phenomenon, I have developed a theory on Parental Intelligence.
Parents actually start out fairly intelligent. They have children, are forced to endure tortuous conditions like sleep deprivation, whine torture, conversation limited to sounds or single syllable words, and the constant drudgery of laundry, picking up toys, and making lunches. Throughout the early years, the tortures parents endure causes a significant drop in cognitive functioning. By the teen years, parents are functioning at their lowest levels.
As children move from their teens into adulthood and leave home, parents are able to catch up on sleep, participate in higher level conversations, and pursue more interesting activities. This allows their brain functioning to recover, thus regaining and sometimes surpassing their pre-child intelligence levels.
Teenagers are correct, their parents are at their stupidest at this stage. Young adults are also correct, their parents actually are intelligent human beings. Easily explained by PIT.