The inability of an individual's social status to change in a school hierarchy. Can also apply to colleges and universities. Usually a consequence of a school environment where cliques are a strong and omnipresent force. Generally results in cliques sticking together for longer than usual, stark contrasts of quality in the social lives of individual students, and close relationships (plus other social luxuries) being limited to the school alpha males and alpha females while those less fortunate are crushed through drudgery such as homework. Antonym of "academic social mobility".
One of the foundations of an elitist "student body" is academic social immobility. Wherever you happen to be in the school hierarchy, whether you be popular and successful or excluded and oppressed, you will stay there for the rest of your school days.