There is considerable variability in the literacy assessments taken in Kindergarten through second grade, across schools and between multilingual learners and other students, and within students over time. This makes it difficult to study changes in students' acquisition of ELA skills in these formative years, or to evaluate policies and practices…

Sources of longitudinal achievement data are increasing thanks partially to the expansion of available interim assessments. These tests are often used to monitor the progress of students, classrooms, and schools within and across school years. Yet, few statistical models equipped to approximate the distinctly seasonal patterns in the data exist,…