Intelligent discussion of schools has disappeared from the presidential campaign, replaced by low comedy, such as Sen. Ted Cruz’s promise to repeal every word of the Common Core State Standards. Cruz would have to persuade many state officials who loathe him to do this, as the standards are largely immune to presidential decree. But his vow passed so quickly that few remember what he said.

For deep insights on the Common Core, the leading education reform of the day, I depend instead on Tom Loveless, a non-resident senior fellow of the Brown Center on Education Policy at the Brookings Institution. Loveless is neither a supporter nor an opponent of the Common Core. He is simply a realist, an endangered political species.

When I hear from teachers and parents who like the Common Core’s enhancement of educational content and emphasis on writing and thinking, I say, “Why not give it a try?” But I also remember Loveless’s studies showing that new standards in general have rarely produced significant gains in student achievement in the countries and U.S. states that have tried them.

In Loveless’s latest annual Brown Center report, new data indicate that the Common Core may already have passed its peak and begun the slow decline into oblivion, to which most U.S. school reforms succumb.

[From the archives: Why Common Core will fail.]

Don’t bother to tell the presidential candidates. They’re interested only in whether the Common Core is interfering with state prerogatives. But those who care about student achievement should consider what Loveless is saying.

He divided the District and the states, including Maryland, which adopted the Common Core, into two groups, strong implementers and medium implementers. He then created a third group, the non-adopters, which include Virginia. He calculated how much each group had, or had not, changed instruction with data from the National Assessment of Educational Progress. The data, composed of federal teacher surveys and student tests, shed light on four Common Core changes: more nonfiction reading in fourth grade, more nonfiction reading in eighth grade, less emphasis on data and geometry in fourth-grade math, and a more unified curriculum in eight-grade math.

As Loveless’s previous studies predicted, the teaching alterations that the Common Core inspired have had almost no effect on student achievement between 2009 and 2015. The new way of teaching “is associated with a change of no more than a single point (plus or minus) in NAEP for both fourth grade reading and eighth grade math scores,” he wrote. “A change of one NAEP scale point is trivial — and especially so over six years.”

Common Core supporters say the effort is just getting started. Loveless summarizes their case: “Professional development, new textbooks, teaching that targets ‘deeper learning,’ and all the other accoutrements of [the new standards] take time to unfold.” He quotes the California State Board of Education chair, who says it will take at least until 2020, a decade after implementation in that state, to see if the Common Core works.

But, Loveless wrote, the data “support a competing hypothesis.” Maybe the new standards program “has already had its best years and additional gains will be difficult to attain,” he said. “Major top-down reforms can have their strongest effects when first adopted, whether it’s the NSF-funded [National Science Foundation] science and math curricula of the 1960s, including New Math, or the more recent No Child Left Behind Act. Policy elites rally around a new policy, advocates trumpet the benefits that will occur,” but schools are not transformed and interest evaporates.

Eighth-grade NAEP math scores declined in 2015 for the first time ever. Loveless said that is probably not the fault of the Common Core, but it still doesn’t look good politically. Which is the point. This election cycle has indelibly labeled the standards as troubled, no matter their merits. It is hard to see how they can survive under such conditions.