This paper is a case study based on Habermas's theory of knowledge and human interest. We analyzed the written reflections of four teachers employed at a school and found that the teachers who had experienced advanced professional development tended to engage in practical and critical reflection, whereas those who had experienced average professional development primarily engaged in technical reflection. Further analysis revealed that teachers who engage in technical reflection experience externally controlled professional development; those who engage in practical reflection experience conservative inner growth professional development; and those who engage in critical reflection experience transcending inner growth professional development.