Help on finding modern choir songs?

hi. i was asked to help my teacher find some choir songs that everyone in our group would enjoy. so i was wondering if anyone new any songs that a high-school choir could sing by miley cyrus, katy perry, demi lovato, selena gomez, justin bieber, miranda cosgrove, carrie underwood, britney spears, hilary duff, etc. artists like that. the songs must be family friendly, but she's sort of a stickler when it comes to pop. so make sure they are songs that a choir could perform and not sound like we were singin in the shower. (: thank you!