There are some excellent resources online. For Charlotte-Mecklenburg Schools, the website is http://www.cms.k12.nc.us. If you're interested in scores and performance, the state website is http://www.ncreportcards.org. Bear in mind that their information is usually a year or two old, since this is the site that houses all public school information for North Carolina. A more objective site that was started by parents and principals is http://www.greatschools.net. Lots of interesting opinions are available there.
Of course, the best way to research schools is to visit them yourself when you're in town.