The case for doing so is based largely on the building's design, which features clusters of classrooms connected by enclosed walkways. It's the city's sole example of this design concept from the 1950s, an era that some architectural historians consider under-appreciated.
Got that? Its historic because it has classrooms connected by walkways. Now maybe that is some huge architectural achievement, but it you are going to argue that the building needs to be preserved because its important as it "features clusters of classrooms connected by enclosed walkways", isn't every building every built arguably historic? Can an abandoned strip mall be "historic, as it features shop fronts connected by a common sheltered walkway, with a parking lot"? I personally think our city would be better served by building density and a property tax base not preserving everything with four walls and a roof. Cities have always been changing, dynamic things (what was torn to build this school by the way?) and we shouldn't let a small group of people's obsession with trying to turn their neighborhood into a frozen moment in time stop us from making our city better. Besides, if we are going to preserve something, lets find something that looks good, not something that looks like a Borg ship.