There do exist some charter schools that really are worth the title of schools. The problem is that there have been far too many shams put in place too, and parents have failed to do their due diligence before making their choices. My brother sent his daughter to a charter school that was tied to the Science Museum of Minnesota, focusing on grades 1-8. He and his wife researched and chose that school because of their STEM focus while also providing solid English, history, etc. courses needed for a well-rounded liberal arts education.
My niece went to that school through grade 6, until they moved to a new area. When she started in public schools at their new home, she was right in line with most other students on most subjects, ahead of them in English, surprisingly.