I suggest each year group should have a "cheer leader " or group rep as you may choose to call him/her.

The task of this figure is to mobilise as many devoted members as possible and bring up their interest in our school activities

Then segregate members voluntarily into these subgroups:
PLATINUM GROUP (To voluntarily raise $500.00)
GOLDEN GROUP (To voluntarily raise $300.00)
SILVER GROUP (To voluntarily raise $100.00)
Bring up your dreams and realities on this topic asap.
cheers