Over the past 30 years, the charter school movement has become a significant factor in U.S. public education. Charter schools were originally designed to be alternative public schools that would allow for greater experimentation and innovation within the public school system. As the number of charter schools has expanded to more than 7,000 nationwide, an active debate has arisen focused on the ways in which charter schools either help or harm the public school system and what should be the appropriate regulation of charter school certification, operation, and expansion.