Significant strides have been made in the research field of early algebra, but more attention to the Mathematics Knowledge for Teaching (MKT) of teachers within this domain is warranted (c.f. Wilkie, 2016; Kieran, 2007). The study described in this paper engaged student-teachers in Germany, Ireland and South Africa in the role of student when they attended a preparation programme for the teaching of functional thinking, and in the role of novice teacher when they taught functional thinking in classrooms. The participants completed pre and delayedpost questionnaires designed to measure their mathematical knowledge for teaching functional thinking. While considerable progress was made by the cohort between the preand post-assessment, challenges persisted on some items. In this paper, we present quantitative evidence of the development in students’ thinking between the pre- and postassessment and discussion of the relatively challenging items.