Teachers' motivation and job satisfaction are widely assumed to shape the quality of classroom teaching, yet the strength and mechanisms of these links remain debated. This narrative review synthesises recent meta-analyses and systematic reviews, mainly published between 2023 and 2026, on teachers in primary and secondary (K-12) schooling. Evidence is organised around motivation theory, job satisfaction and well-being, and the working conditions that sustain them. Across syntheses, higher satisfaction is associated with lower turnover intentions and absenteeism, stronger emotional and instructional support, better classroom management, and more favourable student motivation and achievement, while burnout shows the reverse pattern. Autonomous motivation, competence satisfaction, supportive relationships, and manageable job demands are consistent correlates of teacher well-being. However, most studies are correlational and self-reported, heterogeneity is high, links to student achievement are small and sometimes inconsistent, and the mediating processes remain under-researched. Interventions can reduce teacher stress, but their effects on classroom outcomes are rarely tested. The review concludes that supporting teacher motivation and satisfaction is a defensible but insufficient strategy for improving classroom performance, and it calls for longitudinal, multi-informant research and school-level policies that strengthen autonomy, leadership support, and workload management.