TeacherTube

The first video I watched was Classroom Rules. It had a cop rapping school rules. The first 30 seconds of it were playing music from "Ice Ice Baby" but after that there was no music. I'm sure 30 seconds is less than 10% of the song, so that makes it ok. Also even though it was something funny, it wasn't making fun of the song at all so I don't think it diminishes the value of anything. http://www.teachertube.com/viewVideo.php?video_id=4423&title=Classroom_Rules
The second video I watched was called Crank that GMS. It used the instrumentals from another rap song called "Crank That" by Soulja Boy. Although at the end they gave credit to where the song came from, they used the entire music from beginning to end. I don't think that's allowed and I feel certain they didn't have permission.
http://www.teachertube.com/viewVideo.php?video_id=31041&title=Crank_That_GMS