Third, no common planning time was available that would allow the participating
teachers to meet during the school day throughout the year. After school, conflicts
prohibited using out-of-school time to meet. In-school time was necessary and
substitutes were required. In order to schedule substitutes, full day sessions would
be needed (a day to plan the lesson; a second day to teach/observe, debrief, and
revise the lesson; and a third day to teach the revised lesson and reflect).
Finally, there existed a wide range of mathematical backgrounds of the participating
teachers in the project. To engage in substantive discussions, substantive
mathematics needed to be explored. The facilitators would develop a mathematics
lesson for the teachers to explore the concept before they planned a research lesson
for third graders. The exploratory lesson would immerse the teachers in the concept
before they began the planning process