> Obviously it's not reasonable for a private contractor to have to build a school addition for each housing block (or is it?)
In the UK there have been various methods to get residential developers to pay for infrastructure.
They're fairly recent, and I'm not too familiar with them.
Even if the developer isn't to pay the full cost, there are efficiencies by the local government working with the developer to build relevant infrastructure at the same time.
Example: https://www.telfordhomes-ir.london/media/press-releases/2017...