The Florida Education Association is challenging a proposed state rule on teacher evaluations that would be used in part to determine who gets merit pay.
An administrative law judge was beginning a two-day hearing on the statewide teachers union's objections Wednesday.
The union contends the Department of Education's proposal is vague and arbitrary and does not conform to state law.
The department and State Board of Education dispute those arguments.
The rule is designed to implement a law passed last year. It includes teacher evaluation requirements based heavily on student testing including the Florida Comprehensive Assessment Test, or FCAT.
Besides merit pay, the evaluations would be used to impose sanctions, possibly including dismissal, on low-rated teachers.