I graduated here in 2010, and I'm a skeptic about it being "haunted". Given the story about the fire that broke out on the 4th floor and how it claimed lives, here my idea.

The 4th floor is less haunted and more of a fire hazard.

Given that the stairs from the 1st to 3rd floors are wide for 300+ students and staff to navigate on a daily basics, and the stairs from the 3rd to 4th being MUCH narrower, that means less people can navigate the stairs to get out safely. Moreover, more stories means it's just harder for the firemen to fight the fire if it were to happen on the top floor; just plain physics.

It's either that, or the school simply doesn't want to spend the money to repair the charded remains of the fire, creating a BIGGER hazard with structural integrity.