Learning at the nano-level: Accounting for complexity in the internalization of secondary STEM teacher professional development

•Case study design to explore the lived realities of STEM teacher development.•Current learning models neglect the role of subjectivity and exogenous variables.•Subjectivity provides a useful lens for analyzing processes of STEM teacher change.•Consideration of exogenous variables deepens understanding of teacher PD outcomes.•Understanding complexity could promote improvements in PD research and policy.

Utilizing a case study research design, the factors that influence teacher learning and change, as well as the processes by which secondary STEM teachers internalize professional development (PD) content, are explored. The authors argue that conceptualizations of teacher learning often do not adequately account for teacher subjectivity and the role of exogenous variables in teacher development. The outcomes of PD are heavily influenced by teacher subjectivity, which includes perceptions, previous knowledge, and the internalization of the power and influence present in educational policy and socioeconomic realities. This complexity must be accounted for when planning, researching, or evaluating teacher PD.