I completely disagree with broader point of "cultural reasons" why Asia built high density, because it is all so recent. Mostly in the 1970s-2010s. They built entirely NEW infrastructure, with transit (e.g. subway, highspeed rail), malls, streets, commercial and residential buildings. Look anywhere in Korea, look at the rise of Shin-Yokohama (outside Tokyo), look at the highrise Urbs outside of Paris (out all the way to Rennes).
Why is the center of Paris still only few stories high after the Hausmann era when it was laregely built over 150 years ago. Why don't they put 50 story skyscrapers in Paris... because they don't want to, and they push the "density" to the edges where new facilities can support them. But the housing prices in Paris are astronomical (just as they are in London).
If you want to talk about closing schools, because there aren't children for them... then great! Build new high density where the school used to be. Build a school into the building, put a subway under the school with a connecting mall. Then at least the surrounding neighborhood that has been paying 70 years of taxes doesn't have to deal with the extra traffic/parking of the new construction. Maybe they'll even enjoy the new mall, and foot traffic will help support existing commercial infrastructure.