This paper examines the impact of schools and teachers on student academic achievement, using a unique matched panel dataset from the Harvard/UTD Texas Schools Project. The study aims to disentangle the separate factors influencing achievement, with a focus on the role of teacher differences and other aspects of schools. Key findings include: 1. **Schools vs. Teachers**: While schools have a significant impact on achievement differences, this effect is largely driven by variations in teacher quality. 2. **Teacher Quality**: Variations in teacher quality account for at least 7.5% of the total variation in student achievement, with the true percentage likely being much higher. 3. **Educational Production Functions**: The analysis estimates educational production functions based on models of achievement growth with individual fixed effects. It identifies systematic factors such as initial years of teaching and smaller class sizes for low-income children in earlier grades, but these effects are small compared to the impact of overall teacher quality differences. 4. **Policy Implications**: The findings suggest that policy initiatives must reflect the substantial heterogeneity of teachers to have a significant impact on students. The current institutional structure of schools may not fully leverage the leverage exerted by variations in teacher quality. The study uses a fixed effects, value-added framework to investigate mathematics and reading achievement in grades four, five, and six, controlling for time-invariant individual-specific growth components and various school and teacher characteristics. The results highlight the importance of teacher quality in determining student achievement, suggesting that policy interventions should focus on improving teacher quality and reducing teacher turnover.This paper examines the impact of schools and teachers on student academic achievement, using a unique matched panel dataset from the Harvard/UTD Texas Schools Project. The study aims to disentangle the separate factors influencing achievement, with a focus on the role of teacher differences and other aspects of schools. Key findings include: 1. **Schools vs. Teachers**: While schools have a significant impact on achievement differences, this effect is largely driven by variations in teacher quality. 2. **Teacher Quality**: Variations in teacher quality account for at least 7.5% of the total variation in student achievement, with the true percentage likely being much higher. 3. **Educational Production Functions**: The analysis estimates educational production functions based on models of achievement growth with individual fixed effects. It identifies systematic factors such as initial years of teaching and smaller class sizes for low-income children in earlier grades, but these effects are small compared to the impact of overall teacher quality differences. 4. **Policy Implications**: The findings suggest that policy initiatives must reflect the substantial heterogeneity of teachers to have a significant impact on students. The current institutional structure of schools may not fully leverage the leverage exerted by variations in teacher quality. The study uses a fixed effects, value-added framework to investigate mathematics and reading achievement in grades four, five, and six, controlling for time-invariant individual-specific growth components and various school and teacher characteristics. The results highlight the importance of teacher quality in determining student achievement, suggesting that policy interventions should focus on improving teacher quality and reducing teacher turnover.