Copyright

This week I watched videos about copyrights and learned a lot about "fair use." It seems to me there is a definate line in my major with copyright laws. Between using the media for educational purposes and using the media for enteretainment purposes. My major revolves around creating movement for entertainment value later on. So while in class I am allowed to have my students use music in its full content. But i have a question, If i wanted to have my students take what they have learned and do a concert, where is the lines in that? Say they used a popular song, they are demonstrating what they have learned in class, but then what? I am sure there parents come and record it. I have seen kids performances end up on youtube. It make me think more about teaching my students about correct Copyright.