Assessing the professional identity of primary student teachers: Design and validation of the Teacher Identity Measurement Scale

•We developed a purely quantitative instrument for measuring teacher identity.•Teacher identity is considered as a second-order construct.•Teacher identity was decomposed in four first-order constructs.•These constructs are: motivation, self-image, self-efficacy, and task perception.•qualitative and quantitative scale development approaches were used. This study aimed to design and validate the Teacher Identity Measurement Scale (TIMS) for assessing primary student teachers’ professional identity. Based on identity theory and a systematic review into quantitative instruments of teacher identity, teacher identity was decomposed in four first-order constructs: motivation, self-image, self-efficacy, and task perception. This resulted in a measurement scale consisting of 46 items. The factorial design was examined by administering the TIMS to first- and second-year primary student teachers. In phase 1, involving 17 students, qualitative scale development methods were used to assess the construct validity. In phase 2, its second-order factor structure was tested and confirmed among a sample of 211 students. In phase 3, this structure was cross-validated among a new sample of 419 students. The instrument may contribute to understanding primary student teacher’s professional development and can be used as a tool to support the process of developing a professional teacher identity.