Duluth's Edison charter schools are expanding into three locations this fall, providing spots for a total of 800 students. Their parent company, Edison Schools, Incorporated, a for-profit firm based in New York, is expanding nationally too. This year Edison will operate 77 schools around the U.S. Edison promises better education, But critics say the firm's ability to improve student test scores is still unproven. The company's decision last month to make an initial public offering will likely bring even more scrutiny to its controversial enterprise.