Back in 1988 Ruth Butler did some interesting research on the effects of different types of feedback on the performance of learners. She found that performance improved if she gave learners comments that described what they had done well, and how they could improve on what they had done. But she also found that if she gave grades, then performance deteriorated. And, fascinatingly, if she gave both comments and grades, the results were even worse (see below).
It seems that what happens if you give both a comment and a grade, is that the learner only remembers the grade and forgets the comment (see below).
Butler did her research with school pupils, but the same principle surely applies equally to adults. So, if we really want lesson observation to improve performance (i.e. the quality of teaching and learning) then we need the courage to remove all mention of grades from lesson observation feedback. The way to improve quality is for the observer to simply give honest feedback on what was good about the lesson and in what ways it could be improved. And if the feedback can be the start of an ongoing professional dialogue between the observing practitioners and the observed the practitioner - then that will be even better.
References:
Ruth Butler's research was published as “Enhancing and Undermining Intrinsic Motivation; the Effects of Task-involving and Ego-involving Evaluation on Interest and Performance”,
British Journal of Educational Psychology, vol. 58, pp. 1-14.
The two diagrams above are taken from a PowerPoint presentation by Robert Coe that can be found at www.dur.ac.uk/r.j.coe/learnteach/learnteach4.ppt