Benefits should be benefits to the school, not to the local arts scene, not to the people in the school, not to Singapore, etc....well, it doesn't hurt to benefit these groups...but I think the school's management will be more interested in how the setting up of a jamming CCA is going to benefit the SCHOOL.
For example, through the CCA, people get together, share and learn together, and create bands and groups that go on to represent the school in the National Day Parade, or as guest performer on the MTV Awards, or to be crowned winner of Project Superstars, etc...thereby bringing unheard of glam factor and fame to the school, and the very next year at the school's admission exercises, the queue stretches all the way to AMK MRT (yeah, not YCK!), then I will bet the SA officer will be calling us everyday to beg us to start the CCA...