San Francisco announced and then swiftly reversed a new “grading for equity” initiative last week. The rapid reversal is a sign of a resurgent moderate wing of urban politics — and of a growing anxiety among Democrats that they are losing their traditional status as the party the public trusts on education.

There are many dimensions to this issue, but central to it is the idea that “equity” in education has come to be code for low standards and a lack of rigor. The proposal itself included ideas like making it easier for students to retake tests; excluding factors like lateness and participation for final grades; excluding consideration of homework from grades; and relying on “summative” testing to assess student learning.

Grading for equity sparks intense controversy wherever it pops up, because it sounds to many parents like simply giving up on education and standards for school performance. An indication that Democrats are taking it seriously is the reaction of Rep. Ro Khanna of California, whose Silicon Valley district doesn’t even include San Francisco.

He teed off on an aspect of the proposal that would lower the bar for what it took to get a grade of A, observing that when he scored 90% on a test, “my immigrant dad asked me where the missing 10% went.” The idea of awarding A’s to students who average 80% and don’t do homework, he said, “betrays the American dream and every parent who wants more for their kids.”

The case for grading for equity, it should be noted, is more nuanced than a simple lowering of standards. But make no mistake: There are inescapable trade-offs between the pursuit of excellence and a focus on purely egalitarian outcomes. There is also precious little evidence that faddish progressive ideas about equity actually improve things for students at the bottom.

The “equity” proposal starts with an observation that I sympathize with: When you give kids homework, especially younger kids, you are evaluating the parents as much as the students.

My 10-year-old attends a public school in a once-poor, now increasingly affluent gentrifying neighborhood. The school recognizes that the kids come from a variety of socioeconomic backgrounds, and as a result does not assign that much homework — and the homework it does assign doesn’t count for much.

Taking extra time to practice out of class is important for a child’s learning. But as an assessment tool, it is mostly telling you about the home environment rather than the child. The “equity” perspective on this makes sense to me. What’s more, given the ongoing rise of AI tools and other digital technologies, the whole concept of homework probably needs to be rethought.

All that said, the equity framework doesn’t adequately address the problem.

Go back to Khanna’s comment. His point — and I think most people would agree — is that it is good that the elder Khanna held his son to high standards. It is genuinely unfortunate that not all parents can be as focused and disciplined about this sort of thing, whether because they have to work, have other family obligations or simply aren’t interested. It is important to create positive incentives for both children and their parents to take education seriously and apply themselves.

Meanwhile, the hypothetical student envisioned by the grading for equity movement — the kid who fails to turn in work on time all year but performs well on year-end assessments — seems largely hypothetical. And if she does exist, it’s because she’s a prodigy who could probably be doing even better if she were challenged to do consistent hard work.

It’s hard when a student gets a negative evaluation based on family circumstances outside their control. But many academic assessments evaluate students on the basis of innate talents that are also outside their control. For students to learn, they need rigorous assessments. And the whole point of such assessments is to make distinctions among students, a concept that is fundamentally at odds with a focus on equity.

The good news is that acknowledging this trade-off doesn’t have to mean shortchanging the most disadvantaged students. In fact, the best success stories for low-income kids — whether the “Mississippi Miracle” in reading or the high-performing charter schools — emphasize discipline and old-fashioned educational fundamentals.

These policies don’t necessarily generate “equity” — some kids still do much better than others. But they do deliver better results for kids at the bottom. During the No Child Left Behind era, when Congress held schools accountable for poor kids’ results, the “achievement gap” didn’t actually close because students up and down the spectrum did better. After Congress reversed course on accountability in 2015, results for everyone got worse, even as progressive jurisdictions started adopting increasingly esoteric equity strategies.

Sometimes it’s necessary to state the obvious: Every kid is different, as is every family. The best schools make rigorous assessments and hold students to high standards — and while their outcomes won’t be fully equitable, they’ll be better for disadvantaged kids than those of dysfunctional schools.

Matthew Yglesias is a columnist for Bloomberg Opinion. A co-founder of and former columnist for Vox, he writes the Slow Boring blog and newsletter. He is author of “One Billion Americans.”