PERHAPS BECAUSE of the sunset symphonies of cicadas — or perhaps because of this year’s unusually palatable August weather throughout the mid-Atlantic — nostalgia for the great American summer seems to be running at a record high.

August, as one commentator put it in the Wall Street Journal, is “the very best month of the year,” a time “when the corn is sweet, the plums are purple and pungent, the baseball pennant races are mature, the ocean temperatures are warm. . . . And we have ruined it.” This year, as in others, the annual quest to fix summertime — to revive the halcyon, melon-stained, long-gone America recognizable only in the paintings of Norman Rockwell and in the dinner conversations of the Cleaver family — has resumed.

In a growing number of state legislatures, lawmakers have intensified the perennial push for a later start to the school year, waxing poetic about the good old days. Alabama, Michigan and Mississippi have prohibited schools from starting before the end of August, and Delaware has launched a task force examining the effects of moving back start dates. In Maryland, the pressure is especially strong. Last week, representatives from across the state joined Comptroller Peter Franchot (D) in advocating a post-Labor Day start.

“It’s one of the traditions we should bring back,” Mr. Franchot told the Baltimore Sun. “I almost think starting school before Labor Day is un-American.”

Tradition isn’t the extent of his pitch. Regardless of the costly burden this change would place on working families who’d need to arrange for child care, Mr. Franchot contends that a later start would be a boon to Maryland’s economy, resulting in as much as an additional $74.3 million in direct economic activity and as much as $7.7 million in local and state tax revenue. As the Sun notes, it’s not at all clear where or how the Bureau of Revenue Estimates is getting these figures, and, even if they are accurate, they’d constitute only a marginal increase to the state’s gross domestic product.

As we’ve said before, the costs of a later start to the school year greatly outweigh the benefits. This is 2013, not 1953, and there is no question that summer vacation, as “un-American” as it may be to curtail, contributes to the achievement gap between low-income students and their middle-class and affluent peers. Lower-income students already start school behind andmost students typically lose about one month’s equivalent of learning each summer, no matter where they sit on the socioeconomic spectrum. That adds up over the years, and teachers eventually have no means of closing that gap during the academic year.

Ironically enough, a commonly cited study on this effect is based on data from Baltimore, whose lower-income students would likely suffer even more from Mr. Franchot’s proposed schedule change.

School shouldn’t start any later than it already does. No matter what picture of America lawmakers have mistaken for reality, students in Maryland and across the country deserve the strongest fighting chance they can get.