Research on teacher preparation programs (TPPs) continues to debate whether program quality meaningfully influences teacher effectiveness. Evidence from the United States often reports substantial program-level variation, but the external validity of these findings for other contexts remains uncertain. Using national administrative records and value-added models, this study examines the contribution of TPPs to student achievement in Chile. Results show that TPPs account for only about 5% of the variance in student outcomes. Rather than reflecting uniformly strong preparation, this limited variation reveals a paradox: programs appear remarkably similar, yet convergence reflects alignment around a mid-level standard rather than excellence. Interpreted through the theoretical lenses of teacher learning trajectories, accountability, and equity-oriented preparation, the findings suggest that regulatory reforms may yield uniformity without quality. This study contributes new empirical evidence from Latin America and advances theory by identifying institutional convergence and bounded instructional learning as mechanisms linking accountability reforms to teacher effectiveness.