Z.A.
1) Look into becoming a non-profit.
2) Consider turning your co-op into a homeschool co-op.
...This one is slightly more complex...because any "teachers" you hire, have to;
- be classified as an independent contractor (to avoid having to pay taxes through your nose)
- be free to teach their own curriculum. If you supplied them with the curriculum, and then they had to teach it, they're considered employees.
I'll update in a bit with some helpful links, if others don't beat me to it first!