It depends on each school district and their tax base. Generically, one could easily argue that charter schools are doing better. That is an injustice. The focus on charter schools has left a lot of public schools in poor areas under funded and under served. The students of those schools deserve better.
Charter schools have a mandate to perform in a particular way. They usually structure the program to meet the needs of the particular population they serve. They have smaller classes and expect more from their students. The teachers don't seem as overworked, and this probably has a lot to do with the success of students, too.