Teachers are under scrutiny as never before. Politicians, parents and pupils invest a great deal of capital in teachers' ability to deliver the goods, notably in terms of national test results. In this essay I challenge the view that a teacher's role and value should be defined solely with respect to measurable outcomes, and argue that the influence of a passionate teacher can be powerful, motivating and even life-transforming for pupils. Teachers' affective influence is neglected at its peril, not least because it provides for considerable personal satisfaction and moral agency.