The elite schools patronized by the rich have shown no interest in qualifying as scholarship-redeeming schools. The proposal will take desperately needed funds away from the public schools. The only schools that will lose any funding are those which students want to leave. In fact, that's the whole idea. So on a per student basis, funding will rise.
School choice violates the separation of church and state.
The GI Bill worked because it put decision-making power in the hands of individuals and forced education providers into open competition. Prop 174 extends the same principle to elementary and secondary education. If families are allowed to choose their own schools, American society will ultimately fragment. Most parents care more about a school's educational quality than its complexion. If they can find quality in an integrated environment, a great many would choose to do so.