Unrequited crushes; star-crossed love; bad boys and good girls; sex, drugs, and rock and roll--for generations, these themes have dominated how teenagers are portrayed on film, to the point that they define the teenage years themselves. We take a look back at some iconic films, and how the sweet innocence of Bye Bye Birdie set the stage for today's High School Musical juggernaut; how Blackboard Jungle's tough kids turned into modern-day Mean Girls. The movies may have changed, but the themes are as stubborn as teenagers.