At minimum, the evaluators should conduct one student team observation and team interview once per unit. This will help them gauge if student growth is cumulative across units and if there is transfer of proficiency in data gathering and analysis from one unit to the next. If there are enough resources in the evaluation budget to support it, it would be better to have two or three team observations and interviews each unit, toward the beginning, middle, and end of the unit, to gauge if students get more skilled at their tasks as they progress through the unit.