This week’s “Daily Journal” guest columnist is Terry Stoops, education policy analyst for the John Locke Foundation.

RALEIGH — North Carolina state law requires children to attend school a minimum of 180 days each year, with at least 1,000 hours of instruction covering at least nine calendar months. For years, state education leaders, school officials, and public school advocacy groups have urged the North Carolina legislature to raise these minimum requirements, thereby extending the school day and year.

Our state is not alone. Michael Van Beek of the Mackinac Center for Public Policy recently noted that education leaders in Michigan have been campaigning to lengthen the school day for public schools throughout the Great Lake State.

The idea to add hours and days to the school calendar has also received the blessing of President Obama and U.S. Secretary of Education Arne Duncan. The American Recovery and Reinvestment Act (ARRA) and televised speeches aside, it is the Obama administration’s first meaningful education reform proposal of the post-No Child Left Behind (NCLB) era. If you think NCLB, ARRA, and other initialisms represent federal government intrusion in a state and local enterprise, you should know that there is much more Washington coming to a public school near you.

Proponents of school calendar changes reason that additional learning time will ensure that struggling students do not fall behind in reading, math, and science. They point out that many other nations, including most of the top performers on international tests, have longer school years than public school districts in the United States. Theoretically, the additional time gives students in other nations a competitive advantage over their counterparts in the United States.

While it is true that many high-performing nations spend more than 180 days in the classroom, those students often receive fewer hours of formal instructional per year than students in the United States receive. According to a recent Associated Press article:

Kids in the U.S. spend more hours in school (1,146 instructional hours per year) than do kids in the Asian countries that persistently outscore the U.S. on math and science tests — Singapore (903), Taiwan (1,050), Japan (1,005), and Hong Kong (1,013). That is despite the fact that Taiwan, Japan, and Hong Kong have longer school years (190 to 201 days) than does the U.S. (180 days).

Leave it to the AP then to claim, “Regardless, there is a strong case for adding time to the school day.” Did I forget to mention that the media loves Obama’s proposal to lengthen the school day and year?

There may be a strong case for adding time to the school day and year for struggling students who could benefit from high-quality supplemental instruction. Yet, it does not follow that a universal change in the school calendar would boost the performance of every student or even most students. In fact, some students may receive considerable academic or occupational advantages from a shorter school day and year. Why not give parents the option to send their child to a school with an alternative schedule, which may include longer or shorter days, if parents believe it to be in the best interest of their child’s education?

Research suggests that student achievement is dependent on the quality of instruction — not the length of the school day. The reason is simple. Extending the school calendar without making improvements to the curriculum and teacher quality would simply subject students to additional hours of unproductive instruction. Indeed, high-performing countries are successful because they employ strong leaders, focus on measurable results, and maintain very high expectations for all teachers, parents, and students. Our public schools should focus on the same.

Extending the school day and year is also an expensive proposition. The Expanded Learning Time Initiative in Massachusetts increases instructional time by as much as 30 percent and comes with a price tag of an additional $1,300 per student per year.

In my 2007 Spotlight report titled “Better Instruction, Not More Time,” I calculated that, at the Massachusetts funding level, it would cost taxpayers an additional $656,500 per year to implement a longer school day at a typical North Carolina elementary school. A modest pilot program at five of North Carolina’s 1,800 elementary schools would cost nearly $3.3 million per year. This estimate does not include the increased energy costs required to cool an otherwise vacant school building during the summer or the increased maintenance costs required to keep the building operational for additional weeks or months.

The bottom line on extending the school day and year is straightforward — the federal government and media have no business promoting it, most students would not benefit from it, and our state cannot afford it.

A note about the history of the modern school calendar

In an interview with the Associated Press, Duncan repeated the widely held belief that our school calendar is a remnant of 19th-century agrarian society. Duncan remarked, “Our school calendar is based upon the agrarian economy, and not too many of our kids are working the fields today.” An actual agrarian school calendar would schedule vacations in the spring (during planting) and the fall (during harvesting), not during the summer. After all, in the 19th century, most schools operated year-round. Moreover, vacation periods were not necessary because compulsory attendance laws did not exist in most states. Schoolchildren who needed to work on the family farm during critical times of the year would simply stay home.

So where did the modern school calendar come from? According to education historian Kenneth Gold, groups of concerned educators and physicians conceived of the modern school calendar in the late 19th century and sought to make it the standard for all public schools. They believed that it would be physically and mentally harmful to subject children to months of instruction in unbearably hot and crowded school buildings, thus necessitating a long summer break. This was a response to turn-of-the-century urbanization, not agricultural practice.