Outside of your practice time, you could spend time researching for that favorite song which you would like to sing.
Here are some of the places where you can find music:
Canterbury University Library have a good collection of music scores.
Petrucci music library free classical music scores that are out of copyright.
Sheetmusicplus to purchase music scores.
Amazon great place to purchase music scores.
Naxos Music Library a great place for music listening, they have over 100K recordings available online.
Wikipedia for background information, although sometimes not 100% reliable.
Youtube it’s always good to watch other people performing the same pieces.
Your school library, local music shops, or your friends and family.
The world is your oyster, go and explore!