In traditional studies on value-added indicators of educational effectiveness, students are usually treated as belonging to those schools where they took their final examination. However, in practice, students sometimes attend multiple schools and therefore it is questionable whether this assumption of belonging to the last school they attended can be made. Furthermore, the schools attended earlier by students might have long-term effects on their subsequent performance. Using data from Dutch primary and secondary schools, multiple membership models and cross classification multilevel models were estimated to explore the effects of student mobility and long-term primary school effects on the estimated value added of secondary schools. Long-term effects of primary schools did not change the estimated value added of secondary schools. On the other hand, allowing students to be a member of multiple secondary schools changed the estimated effectiveness of these schools especially for schools in the middle range of effectiveness. (Contains 5 tables and 1 figure.)