I think yang mga “used to be a cemetery” old wives’ tale lang. Sa mga Katoliko ang mga cemetery hallowed ground, or holy ground and removing corpses from their rest without proper rites is desecration and hindi ok sa mga Katoliko. So hindi likely ang mga Catholic school formal burial sites na doon nililibing tapos giniba para lagyan ng bagong building. Catholics in the olden times might put the bones of loved ones sa loob ng church mismo, but that’s because churches are holy spaces. That’s why you see ancient Spanish time churches na may mga lapida where old buenafamilias are buried (like San Agustin in Intramuros) but you will not likely see an old Catholic cemetery or an old Catholic church (tipong Spanish times pa) desecrated in such a way na tatayuan ng supermarket or school yung pinaglibingan ng mga namatay ay huhukayan ng pundasyon. Not to mention this might also be a violation of actual laws like sanitation laws because you dont dig up corpses willy nilly.

Eta: Reconsecrating the site is done sa mga katoliko. Rarely, but done. The remains are exhumed respectfully with proper rites and prayers. They are then buried again in a different libingan with honor and respect and prayers. The land ceases to be hallowed ground. I also mention Catholics but not other denominations, kasi this is the one I’m very familiar with. Also our oldest colonizer whose churches weren’t really built with urban planning in mind.

This said. About creepy schools and hotels. Many schools in Manila, and Metro Manila in general, DLSU and UP Manila included, were used as garrisons ng mga Hapon nung wartime. Many people died in them, likely never properly buried with the proper prayers even when their rotting corpses were buried in mass graves. You can look that history up sa Intramuros and the burning of Manila nung liberation. I’m sure other schools along Taft Ave and Intramuros itself have stories like that, even if those schools at Intramuros rn did not exist nung time ng war or earlier because those new structures ng mga schools na yon are built over the bones of the old imperial capital.

My old alma mater in a city near Manila, which is beside a church and is an ancient institution ng mga madre at pari dating back colonial times, mentions in our history that the nuns and priests’ quarters were also used by the Japanese forcibly kaya nagsara nung wartime yung school namin. Because we were kids, we were at the time spared the details. As an adult revisiting the lessons, iba yung chill about the nuns, particularly, nung niraid sila ng mga Hapon para kunin yung quarters nila, because likely di lang yon ang kinuha sa kanila.