Teacher tenure provides job security for teachers after completing a probationary period, making it difficult to dismiss them without cause. Supporters argue it protects experienced teachers from arbitrary firing and encourages them to advocate for students, while critics argue it allows ineffective teachers to remain in classrooms. Research shows dismissing ineffective tenured teachers through the legal process is difficult and expensive for school districts. When budgets are cut, seniority-based layoffs protect longer-serving teachers over less experienced but potentially more effective ones. The effects of ineffective teachers on student achievement are significant.