Here's a spot-on editorial from the Chicago Tribune:

We're huge fans of charter schools. We want to see more of the best charter school operators come to Chicago.

But the schools and the operators have to prove their worth. They don't get a pass because they have the golden name "charter." If some don't raise the educational achievement of Chicago's children, they should be reconstituted or closed. Make room for new schools, new operators, new ideas.

Chicago Public Schools CEO Jean-Claude Brizard said Wednesday that CPS will force major changes at two underperforming charter schools, changes that ultimately could lead to closing them. A third, Chicago International Charter Schools' Basil elementary campus, will go into turnaround. That's a last-ditch option, short of closing, in which CPS replaces school leadership and staff and revamps curriculum.

That suggests CPS leaders understand that charters must be held to the highest performance standards.

Now, Andrew Broy, head of the Illinois Network of Charter Schools, warns about the limitations of the state charter data.

He argues that charters should be judged not on a single standardized test score, but on the trajectory of student growth over time. Broy says that 17 of 26 Chicago charter high schools showed better growth in student achievement this year than the average traditional high school.

That's great news for students and parents in those 17 schools.

And it says that students and parents in the other nine schools ought to be asking a lot of questions.