A Cass County school district’s effort to get and keep some teachers in fields that are hard to find teachers to teach has triggered a lawsuit by the National Education Association. The Sherwood Cass School District is paying $1,000 and $2,000 bonuses to the teachers, who have signed two-year contracts. But the NEA says the deals violate the state teacher tenure law, which requires uniform salary schedules for all teachers, and violates the agreement the NEA has with the school system.