I'm a fan of "common pot" but it doesn't work as well as one might like: in the public schools here in Palo Alto the parents routinely hold auctions that raise multiple millions of dollars which goes into paying for things that I think every kid should be getting (art, PE, music, an aide in the classroom etc).
PTA donations got so extreme that the school district had to implement the same "one pot" approach just to spread the money around the schools in the Palo Alto school district.
Palo Alto district is a basic aid district. This means that they get no money from the state...they have parcel tax to fund their schools. Palo Alto is a wealthy enclave in CA. They don’t have to deal with the restrictions of other counties and school districts.
[..]Some districts, known as “basic aid” or “excess tax” districts, fund their revenue limit entirely through property taxes and receive no general purpose state aid. They also retain any excess property taxes within their district. ... Basic aid districts are generally more advantaged than other districts.[..]
PTA donations got so extreme that the school district had to implement the same "one pot" approach just to spread the money around the schools in the Palo Alto school district.