Well, you've heard from someone telling you one side about charter schools. But there is another side.
Charters tend to have very little, if any supervision on the part of either the NYC Dept. of Education or the State Dept. of Education. Many are very corrupt. Several have been closed down for corruption, including a woman who hired her own husband, paid him a huge salary for doing nothing, and using the school as her personal piggy bank. (She's probably going to jail. This happened in NYC, btw.)
Also, even very good charters tend not to take kids with special needs or kids who are second language learners. This means that public schools get a higher proportion of these kids. Yet, many charters, even without these kids, are only doing about as well (or sometimes worse) than equivalent public schools.
Are there some great charters? Sure. But there are many great public schools as well. And there are many lousy public schools, but there are lousy charters as well. They just have to go really wrong before anyone realizes it, because of a lack of supervision.
My last problem with charters is that often they derail real reform of ordinary public schools. Harlem is a great example. There was real reform going on in Harlem schools in the 1980s and it was starting to make some progress in a few schools. Then the charter movement came in and all of the efforts at reform of the regular public schools died on the vine. So the regular public schools actually got worse as the charters came in. Such a shame!
Bottom line, charters are not the panacea for problems in education. We'd be better off finding what works within the regular public schools.