This article presents findings from a study of performance management in 10 schools, five primary and five secondary. The aim was to gain a snapshot of how headteachers are interpreting and implementing the reforms to the performance and capability procedures for teachers introduced in September 2013. The findings suggest that the evaluation of teachers is conducted within a context of normalised visibility with evidence of competence collected via observations, learning walks, electronic data, organisational and architectural structures. However, this normalised visibility is contrasted with the normalised invisibility of the actual processes of judgement such as appraisal. Invisibility also frames the management of incompetence, with poorly performing teachers routinely offered "compromise agreements" to avoid the official capability procedures. The article concludes by highlighting the limits of the panoptic metaphor in a consideration of teacher evaluation and discusses an alternative metaphor, that of glass, with which to view the performance management of teachers.