This paper documents how a team progressed through the five stages of team development as a result of a school-based professional development program using a laboratory class cycle. Six Grade two teachers and their administrator in a primary school in the southeastern United States participated in the study. All the teachers were interviewed at the end of each laboratory class cycle. Their administrator was interviewed after the program ended. A grounded theory approach and constant comparative method were used. The study revealed how the teachers' participation in the program progressed according to Tuckman and Jenson's (1997) model of team development in the laboratory class cycle. Establishment of trust among teachers and team support over an extended time were identified as important factors in shaping the team development. (Contains 1 table.)