No one seems to have much love for the No Child Left Behind Act these days. But everyone seems to agree on the best feature of the law: Schools now have to show how student subgroups that historically were ignored (English-language learners, racial minorities, economically disadvantaged students) are doing relative to their peers.

But it sounds like some civil rights and advocacy organizations are worried about that part of the law being weakened in the upcoming reauthorization of the law, as policymakers try to give states more flexibility overall.

Now a long and varied list of advocacy groups, including Democrats for Education Reform, The Education Trust, the Center for American Progress Action Fund, the National Council of La Raza, the NewSchools Venture Fund, and the U.S. Chamber of Commerce have sent a cautionary letter on that subject to U.S. Secretary of Education Arne Duncan and lawmakers overseeing reauthorization on Capitol Hill.

Here’s a snippet from the letter:

Here are some of the policies the groups want to see in the new version of ESEA:

1) All students be held to the same college- and-career ready standards, regardless of subgroup.

2) Proper adaptions, accommodations, and assessments be maintained for students with disabilities and ELLs.

3) States continue to set annual, measurable, and ambitious goals for the academic growth and performance of all students and for closing achievement and graduation gaps between all students and subgroups, including economically disadvantaged students, racial minorities, and ELLs.

4) Districts be held accountable for supporting schools and closing district-wide achievement gaps.

5) States and districts make transparency “paramount,” and parents be given a right to know how their children are performing.

Why this letter now?

Advocates have been worried about some of the signals they’ve seen lately from the administration on this issue, most notably the claim that more than 80 percent of schools are “failing,” a statistic the administration says is unfair and an indication of why the law needs to be updated.

But many of those schools are being labeled as not meeting achievement targets because of subgroup performance, advocates say.

Raul Gonzalez, the director of legislative affairs for the National Council of La Raza, told me in an interview last week that he does “believe the administration is committed to closing gaps.” But he worries that without strong subgroup accountability, states and districts might not focus on schools where minorities and special populations (such as ELLs) are lagging behind their peers even though the schools are doing well overall.

“If I’m a state and I have limited funds and hard choices to make, if there’s hard accountability for the bottom 5 percent, that’s where I’m placing my emphasis,” he said. “There’s a lot of uncertainty. We’re not in a place right now where we’re comfortable with where ELLs may end up with regard to accountability. ... It’s important for the administration to clarify what they mean” when it comes to subgroup accountability.

The department just received the letter today, so I’m guessing officials haven’t had a chance to comment. But here’s what Sandra Abrevaya, a spokeswoman for Secretary Duncan, told me last week when I asked about the subgroup issue: “Subgroup accountability is critically important to the department. We frequently highlight schools that have made gains across all subgroups.”

She added that Duncan “says consistently that the most important thing that NCLB did was to create subgroup accountability. That’s one of the things that we’ve time and time again said we’re going to maintain.”