School choice increases quality in other public schools, according to a North Carolina study published by the National Bureau of Economic Research.
Most charter schools opened in metropolitan areas, and 90 percent of district schools were within 13 miles of a charter school. The authors find that charter school competition raised the composite test scores in district schools, even though the students leaving district schools for the charters tended to have above average test scores. The gain was relatively large, roughly two to five times greater than the gain from decreasing the student-faculty ratio by 1, and more than “one-half of the average achievement gain of 1.7 percent in 1999-2000.”
For comparison, the authors point out that the North Carolina Governor’s Office proposed increasing achievement by reducing average class size by 1.8 students at a cost of $26 million in 2002. The data suggest that this would produce just one-third of the test score increase created by opening a neighboring charter school, a move that would not require any additional spending.