Forum 4: Compare the achievement trends of a true cohort and a quasi-cohort

In Figure 3, in my paper on longitudinal achievement trends, you are shown a longitudinal comparison of achievement for a true cohort and a quasi-cohort of students over Grades 1-6 over six years. Over the years, the achievement levels of the true cohort have declined rather steadily. While initially slightly below the true cohort, the achievement of the quasi-cohort improved to a level above the true cohort, where after it declined rather precipitously to a level four points below the true cohort. Using the corresponding enrollment data (Table 4) over the same years, attempt an explanation for the achievement trends of the two groups. In other words, try to explain what is going on? You can work independently, in groups (just, when responding as a group, indicate the group membership), or both. However, you should use the commentary of each other in solving the problem. I will give you my explanation after most of you have responded. Good luck!