Avoid playing songs as time fillers. Use good quality recordings. Also, be sure to use a good and sufficiently powerful cassette or CD player. Set the cassette at the exact point where the song starts, avoid looking for the track beginning in class. Most textbooks now include songs in their lesson plans, but if your textbook does not include them, do not worry.
Popular songs are a good source for our purposes.
There you will find links to other lyrics pages.