With respect to evaluating students' and teachers' performance, a distinction is made between assessment for learning and assessment of learning. The former aims at determining how the student can improve to the best extent and the latter at determining how good the student is. These different aspects have considerable implications for the approach to the evaluation of the validity of an instrument. The 'Systematic evaluation of teaching qualities' (SETQ) instrument may be seen either as assessment of performance (learning) or assessment for performance. In a recent study Lombarts et al. focused the validation procedures more on the assessment of performance (of teachers). It is notable that the other approach (assessment for learning) is becoming more popular in the assessment area. If the SETQ is viewed as an instrument for performance improvement, one wonders whether a factor analysis as carried out by Lombarts et al. is the best validation approach or whether possible judgment biases should in fact be the subject of research. In addition, the qualitative comments are more relevant than the numerical outcomes.