How long can you use a song before having to get copywrite permission?

I'm working on a project for school, and it will be aired on our school news program. I want to put in a cool song, but I'm not sure how long I can use it for. If I remember correctly, it's only 30 seconds. I can't simply put in "The Final Countdown - Europe" at the end, can I? It would make it a lot cooler lol thanks