The effectiveness of teaching is cited as one of the most significant actors on students’ learning (Centra, 1993; Creemers, 1994; Marsh, Nagengast, Fletcher, & Televantou, 2011), yet the measurement of it is an imperfect and problematic activity, not least due to the lack of consensus over a definition of effective teaching and, consequently, no consistently-used measurement instrument(s) designed for the purpose (Chingos & Peterson, 2011; Goldhaber & Anthony, 2004; Kane, McCaffrey, Miller, & Staiger, 2013). This thesis describes a study designed to validate an instrument intended to capture secondary school students’ evaluation of teaching (SET) ratings in 36 UK schools during the 2012-13 academic year, and a randomised controlled trial (RCT) to evaluate the impact on student progress of a peer-coached consultative feedback intervention for teachers. The thesis concludes that the SecondarySEEQ instrument is valid and reliable for the purpose of capturing AS and A Level students’ perceptions of the quality of teaching they receive from their teachers, a finding which adds weight to the case for SETs as a useful component of a diagnostic feedback system for teachers. I also conclude that the peer-coached intervention had a no detectable effect on student outcomes.