The Wisconsin Institute for Law and Liberty (WILL), which does great work, has written U.S. Secretary of Education Betsy DeVos, urging her to withdraw an Obama-era “Dear Colleague” lettergiving school administrators “guidance” on how to comply with federal law when it comes to school discipline.

Threatening lawsuits if the administrators didn’t comply with the “guidance,” the 2014 letter coerced many school systems into adopting illegal racial quotas in their disciplinary decision-making.

The Obama letter utilized the “disparate impact” approach to civil-rights enforcement, whereby a policy that does not discriminate on its face, in its intent, or in its application is nonetheless deemed illegal if it has “disproportionate” statistical effects among different racial and ethnic groups.

A number of other organizations, including the Center for Equal Opportunity, joined on WILL’s letter to Secretary DeVos, which continues the steady drumbeat on this important issue from conservative groups. Here’s hoping that she withdraws the discipline letter soon, as she correctly did with similar letters by the Obama administration regarding sexual harassment on college campuses and transgender students in school bathrooms.

Certainly, there is no lack of reasons to withdraw the letter, which created both legal and policy problems. Procedurally, it violates both the Congressional Review Act and the Administrative Procedure Act. Substantively, as the WILL letter explains, the Education Department lacks authority to use the “disparate impact” standard in enforcing Title VI of the 1964 Civil Rights Act, which prohibits discrimination in programs or activities that receive federal funds. In 2001, the Supreme Court ruled in Alexander v. Sandoval that Title VI bans only “disparate treatment.” In any event, the letter’s hyper-aggressive approach violates other Supreme Court and lower federal-court decisions, including a ban on racial quotas in school discipline.

As a policy matter, there is overwhelming evidence that Obama-era policies culminating in this “Dear Colleague” letter pushed schools to avoid disciplining students who needed to be disciplined. It made avoiding politically incorrect numbers more important than maintaining school safety.

The victims of this unfair and unlawful policy are most likely to be well-behaving, minority students — and their teachers — whose classrooms become disrupted and dangerous. And it doesn’t do misbehaving students any favors either, since a lack of early corrective action may only encourage even more disruptive and potentially dangerous behavior. This is what some refer to as the school-to-prison pipeline.