Student teachers are expected to develop their teaching skills sooner and more rapidly. However, a sound evaluation instrument that can be used to diagnose and monitor the skilfulness level to aid formative assessment of student teachers is still limited. This article is aimed to calibrate and validate a teaching skill evaluation instrument for use in secondary education. A total of 264 student teachers in the Netherlands participated in the study. Rasch and multilevel analyses were used. Results suggest that the evaluation instrument meets the restrictive assumptions of the Rasch model and has predictive value for academic engagement. This adds validation evidence and justifies the calibration of the evaluation instrument to be used for monitoring the development of teacher's teaching skills.