Background: After elementary school, students in Germany are separated into different school tracks (i.e., school types) with the aim of creating homogeneous student groups in secondary school. Consequently, the development of students' reading achievement diverges across school types. Findings on this achievement gap have been criticized as…

When competence tests are administered, subjects frequently omit items. These missing responses pose a threat to correctly estimating the proficiency level. Newer model-based approaches aim to take nonignorable missing data processes into account by incorporating a latent missing propensity into the measurement model. Two assumptions are typically…