If a student is moved from one class section to another or removed from a class section and then placed back into the same class section, the student's diagnostic results are not saved because this student's data is tied to a larger data-set (ie, the other students' diagnostic results) which is connected to the original class section in which they were initially placed.  Once a student is placed back into a class section, that student then has the opportunity to complete the diagnostic assessment assigned to the class section into which he/she is placed.