In a private subdivision, there are certain areas there that can be donated to the local government like the roads. Those are the usual spaces being donated to the local government.
Because you can see even in a private subdivision, the local government is pay for the electricity because they have post there. So, those are the usual spaces that can be donated to the local government.
If the open space refers to a property that has not been donated to the local government and the local government is constructing a public school there, then, there is a violation. Unless the local government would expropriate that.
May "expropriation", ang ibig sabihin nito, this is the process under the law where the government has to buy the property from the subdivision. Meaning they can't just take it away and start building a school there without buying a subdivision. And also this requires a procedure. They can't just do it overnight and say we're getting this and we're building a school here. It has to go through court proceedings, what they call expropriation proceedings. Meaning they have to prove the necessity to use that lot or land for building a school and they have to pay just compensation. The price has to be fair. Hindi pwedeng makakuha sila ng malaking discount because they are the local government. Not necessarily at a fair market value. It could be lower but it should be fair.