First of all, I'd like to commend you on the effort put forth in “unionizing” the classroom. If it was something for marks, you'd absolutely get full participation for your endeavours. There are, however, some glaring issues with what you are trying to accomplish.
There are in fact 50 students in the class, not 39 as you've stated.
You cannot unionize a classroom. Unionizing is a form of protection that workers can use to ensure they are treated appropriately, paid accordingly, scheduled properly, and all around ensures they get a “Fair day's wage, for a fair day's work.”
Unionizing, is intended for EMPLOYEES, to protect themselves.
Not for students to parade a sense of entitlement and ignorance to the very core concepts of