This study explores the use of Valsiner's zone theory as a way to interpret the zones of proximal development of three secondary teachers in mathematics and science. Specifically, we used classroom discourse to identify what the participating teachers promoted (zone of promoted action) or allowed (zone of free movement) in the classroom as a way to understand better their potential for development. We found that teachers who promoted actions or events that they ultimately did not allow students to experience seemed to be at a point in their development analogous to Vygotsky's pseudo-conceptual stage, prior to full concept formation. Moreover, we found that, at this "illusionary zone," the teacher's capacity to listen actively to students thinking seemed to affect the teacher's transition toward more inquiry-based forms of practice. We concluded that understanding the zone of promoted action and the zone of free movement the teacher organizes in the classroom can indicate the existence or absence of an illusionary zone and thereby provide insight into a teacher's potential for development.