There is a partial exemption to the licensing requirement for music as part of a religeous service (not dancing). Any other musical activity in a church, paid or otherwise would be considered as public entertainment and require a PEL. There is an oficial reply on the the subject, posted here somewhere.

The others depend on if the public have normal access to the premises where the activity is taking place. During normal school hours, the public do not have access. In the evening, a PEL would be required, if the public were freely admitted.