Multilevel modeling of educational longitudinal data with crossed random effects

We consider multilevel models for longitudinal data where membership in the highest level units changes over time. The application is a four-year study of Korean students who are in middle school during the first two waves and in high school during the second two waves, where middle schools and high schools are not nested. The model includes crossed random effects for middle schools and high schools and can be estimated using Stata¡¯s xtmixed command. An important consideration is how the impact of the middle school and high school random effects on the response variable should change over time.