This paper estimates the importance of teachers in UK primary schools using matched pupil-teacher survey data. The results show that teachers are important inputs in pupil cognitive skills (measured by math test scores) as well as non-cognitive skills (measured by emotional health and social-behaviours). In addition, teacher ability to improve math test scores is weakly correlated with teacher ability to improve non-test score outcomes. I then decompose these measures of teacher effectiveness into different teacher characteristics. Teacher satisfaction and teaching practices (including class streaming, homework, types of incentives used, etc.) contribute more to explaining the variation in estimated teacher quality (up to 25%) than is explained by traditional observable characteristics such as teacher gender or experience.