A retired teacher volunteers at the front desk of the school where I am working temporarily. She told me how her mother, also a teacher, was once paid with "warrants". I asked her what the meant. Essentially, a warrant was an IOU. When the school district did not have sufficient funds to cover payroll it issued warrants. Warrants were paid off in the order that they were issued as funds became available. How can you live with an IOU? You don't. You sell the warrant/IOU to a bank or other philanthropist for $.50 to the dollar who later redeems the warrant at full value.
I imagine that the retired teacher's mother was not represented by a union. Unions and collective bargaining rights are essential and necessary to ensure that no teacher is ever compensated by warrant again ... Do you think warrant-like payments couldn't happen again? I'm not willing to find out.