Charter school funding

I'm a little slow on the uptake, but this Albany Times Union column from 5/23 makes a good point:

We need direct state funding of charter schools, not financing that comes from traditional aid to the districts. Charters may be public schools, but they are redundant public schools. They're an experiment. Those advocating the experiment should find a way to pay for it that doesn't cripple the local taxpayer.

Personally I'm of the opinion that all school funding should come directly from the state (outside of Title funding, etc.). But why not start with charter schools? I know there's some reason charter advocates give, I just can't remember what it is right now.