I’ll hazard a guess that someone used the information inappropriately… sent solicitations for a charitable event (which had nothing to do with the school), shared the information with outsiders/outside organization, someone with nefarious intent is using the information, etc.
I know several private schools have recently had to tighten up their data practices. No organization wants the liability or the headache if there is a problem with their privacy controls.
My suggestion is to approach the administration to ask if there could be an opt in/opt out process? So that parents who want to participate have their information showing- and likewise, can see the information of others who also don’t mind?
For all you know, someone’s famous parent is being stalked or harassed by a stranger and law enforcement suggested that they remove all publicly accessible personal information…
But the administration may be willing to help you with a workaround…