Making validation clearer for classroom teachers

For four years I have taught in a wide variety of schools and I have always been confused about how we use the word 'validity'. I knew the word had something to do with 'goodness', but goodness of what? And how could I know what was good and what was not? That is what motivated me to enrol for the University of Cambridge postgraduate certificate in educational assessment and examinations. On this course I examined issues in assessment such as validity, validation, reliability, fairness and bias. I also came across Michael Kane and, in particular, his work with Terry Crooks and Allan Cohen (Crooks, Kane and Cohen, 1996). Of all the readings I reflected on during the course, this provided an answer to at least one of my two central questions and supported the development of assessment in my department and school. Although other popular assessment books such as Daisy Christodoulou's Making Good Progress? (2017) present validity in fairly concrete, black-and-white terms, my postgradu