Another school year has gradually kicked off across America, with virtually every school in session now that Labor Day has passed. The return of school renews debate about how long the school year should be, and how standardized it should be across regions.

While educators debate the merits of year-round schooling, administrators across the country continue to tinker with the school calendar. In Akron, Ohio, LeBron James’s foundation has opened a school that includes a seven-week summer session. In metropolitan Chicago, two local districts switched to a fall semester that mirrors the college model. In Philadelphia, the district moved the start of the 2018-2019 school year to before Labor Day.

But most of the debates over the contours of the school year are premised on the historical myth that summer break stems from a time when children needed to work on the farm — a myth that biases these debates and ignores the challenges that prompted the introduction of summer vacation and that still exist today.

In the early 1800s, agrarian communities generally operated public schools for a winter and a summer term of two to three months each. The spring and fall, labor-intensive times for farming, featured no school. During the summer — no less important an agricultural season — older children were typically absent from school, since families counted on their labor.

At the same time, urban school systems were developing with different needs driving the calendar. New York, for example, reported 49 weeks of schooling in 1842, a figure similar to the 11 months in Baltimore and the 251.5 days in Philadelphia. These and other cities divided the school year into four quarters, and summer terms attracted comparable numbers of students to the others. But as in rural areas, the need for labor and the absence of compulsory education laws kept vast numbers of school-age children from attending classes all year.

For both rural and urban districts, these patterns changed by the end of the 19th century.

In many cases, officials never formally set out to rethink the school calendar. Rather, year-to-year exigencies — ranging from fiscal limitations to popular pressure to have holidays off — led to school-year reductions that, once undertaken, were difficult to undo. While reformers worked hard to increase overall student attendance, school officials grew weary of opening schools on days when large numbers of students were not present, driving the length of the school year down.

A push for standardizing school calendars also contributed to a shift toward summers off. Nineteenth-century urban school systems were not yet centralized, and the school year varied maddeningly from ward to ward. In New York, for example, ward schools ranged from 231 to 244 days of school in 1844. Citywide figures who wanted uniformity between local wards often had to settle for the lowest common denominator when it came to school-year lengths.

The summer was the obvious place for most of these cuts. Wealthy urban inhabitants had traditionally vacated American cities during the hot summer months, a practice that expanded to the middle class in the 19th century. School buildings with poor ventilation were especially unbearable during the summer, and attendance did tail off toward the end of the quarter. In response, cities such as New York gradually extended the August break until it included all of July as well.

There were also handy ideological reasons for prolonging summer vacation. Foremost were medical and popular beliefs about the frailty of the human mind and body that translated into real fears of overexertion by students and teachers. Summer vacation was heralded as an opportunity for mental and physical rejuvenation, and school officials hastened to reassure taxpayers and parents that teachers would benefit professionally from additional training during the summer.

In rural areas, reformers such as Horace Mann wanted lengthier but also standardized school calendars. They aimed to make the school year longer, for example, than the five-month average found in Michigan in 1840.

But they too agreed that a longer school year did not require a summer term. They viewed the summer term as inferior to the winter one because it attracted younger students and was commonly taught by young women, as opposed to older men, whose quality also ranged widely. Using legal, financial and bureaucratic mechanisms, they prodded districts to add school days and to reconfigure the school year.

By the onset of the 20th century, then, urban and rural public schools were both converging on the now standard 180-day school year with a sizable summer vacation. Concerns about the potential for urban youth’s idleness and mischievousness without school, particularly as they increasingly arrived from Eastern and Southern Europe, gave way to budget realities. Year-round public education seemed too expensive.

It is easy to misconceive summer vacation as a simple product of agrarian needs rather than this more complicated story of demands for standardization, teacher professionalization, budget problems, lax attendance and fears of overburdening students. And this historical inaccuracy matters. The misperception leaves today’s reformers fighting the wrong battle, while conceding that the school calendar is something that deserves deference as if it was carefully constructed with best practices in mind.

By misidentifying the roots of the current calendar, reformers fail to grapple with the fact that the same factors — budget crunches, demands for time off, concerns about over stressing students — still exist today. And absent addressing them, efforts to change the school year are likely to fail.

The push for year-round school is often based on the desire to ease overcrowded urban systems or to make more efficient use of school facilities. But it is also supported by 40 years of research that corroborates what teachers have long known: students lose knowledge over the summer. This dynamic, however, actually compounds the difficulty confronting reformers.

Wealthier parents regularly exercise options such as enrichment programs, summer camp and travel abroad for their children, ultimately making summer learning loss highly correlated to socio-economic status. But since summer school costs money, it requires an investment in the public sector, something policymakers seem reluctant to do in our current climate.

But the cultural hurdle might actually be reformers’ biggest challenge. One hundred twenty years of summer vacation have encouraged rich and poor, white and people of color all to participate in activities centered on summer vacation and warm weather: Fourth of July fireworks, baseball games, outdoor concerts, amusement parks, summer camps and camping, barbecues, hours by the pool, days at the beach, weekends at the shore and months abroad.

Increasing summer school may be a good educational policy for raising standardized test scores or increasing graduation rates, but is it good social policy to tamper with the season during which many families and friends forge their most enduring bonds and memories, and where students get a break from the stresses and pressure of schooling? Summer learning opportunities should be abundant for all children, but they need not look and feel so much like school.