This fall, more students than ever will head off to public charter schools as the school year begins. Approximately 2.5 million students will enroll in 6,500 charter schools across the country. Notably, from 2001 to 2011, charter school enrollment increased by 1.2 million students.

Charter schools, which are public schools that are independently managed and operated, have grown in popularity in recent years. Part of that popularity may be due to the schools’ productivity and ability to improve learning outcomes on a more limited budget than traditional public schools enjoy.

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Researchers Patrick J. Wolf, Albert Cheng, Meagan Batdorff, Larry Maloney, Jay F. May, and Sheree T. Speakman recently examined this question in their article The Productivity of Public Charter Schools. Wolf and his coauthors found that:

“…the public charter school sector delivers a weighted average of an additional 17 [National Assessment of Educational Progress] NAEP points per $1,000 invested in math, representing a productivity advantage of 40 percent for charters. In reading, the public charter sector delivers an additional 16 NAEP points per $1,000 invested, representing a productivity advantage of 41 percent for charters.”

Wolf and his coauthors also found that lifetime economic earnings obtained in charter schools outpaced those of traditional public schools. “In all states,” the authors note, “charter schools deliver a greater [Return on Investment] ROI than do [traditional public schools] TPS.” Not only do charters deliver a greater return on investment, but in 18 of the 31 states evaluated in the study, charters also enrolled more disadvantaged students than did traditional public schools:

“Any claim that the higher productivity of charters relative to [traditional public schools] TPS is because charters serve a more advantaged population would be undermined by these findings, as all charter sectors outperform their [traditional public schools] TPS on productivity measures even though half of the charter sectors enroll a more low-income population of students than their TPS.”

Why are charters so cost-effective and productive? “It appears to be likely that much of the basis for the higher productivity of public charter schools rests on the fact that they receive less funding and therefore are highly disciplined in their use of those education dollars,” the authors surmise.

“Our analysis indicates that charter schools are consistently more productive than traditional public schools across both cost effectiveness and return on investment calculations for all the states in the study,” Wolf and his coauthors conclude.

Stanford’s Caroline Hoxby has also studied the effectiveness of charter schools at length. In a multiyear evaluation of charter schools in New York City, Hoxby found that attending a charter school from kindergarten through eighth grade would bring disadvantaged students up to the level of students in affluent suburban schools in mathematics, and would close 66 percent of the achievement gap in English. Charters produce a “major and lasting difference,” and accomplish what Hoxby refers to as a narrowing of the Harlem-Scarsdale achievement gap, or the gap between affluent districts and lower-income areas.

A 2010 U.S. Department of Education evaluation of the impact of charter schools also found higher levels of satisfaction among parents with both the quality of schools and their child’s development.

Across the country, more children than ever now have access to schools of choice. Charter schools represent a major part of the growth in school choice over the past decade, with just 8 remaining states still barring charter schools from operating. And with the average charter school having a waiting list 300 students long, it’s time every state allow these flexible public school options to serve families.