Are Chicago Public Schools the Worst in the Nation?

The Chicago Sun-Times present some facts to suggest that the Chicago public school system are the worst in the nation:

Only 54 percent of Chicago public high school students who started in 1999 graduated by 2003.
Most Chicago Public Schools alumni must take remedial classes at the Chicago City Colleges; 74 percent must take remedial English; 94 percent must take remedial math.
Grade inflation: 75 percent of CPS students who earned a B average scored below a 20 on the ACT. The national average is 20.9.

So what's the reason to have high taxes to support the worst?