The issue of the discipline guidance was raised formally by Senator Marco Rubio, Republican of Florida, who, after seeing a flurry of conservative news media reports, wrote a letter to Ms. DeVos and Attorney General Jeff Sessions questioning whether the guidance allowed the shooting suspect, Nikolas Cruz, to evade law enforcement and carry out the massacre at Stoneman Douglas High.
It was, on its face, an odd point: Mr. Cruz is white, and far from evading school disciplinary procedures, he had been expelled from Stoneman Douglas.
“The overarching goals of the 2014 directive to mitigate the school-to-prison pipeline, reduce suspensions and expulsions, and to prevent racially biased discipline are laudable and should be explored,” Mr. Rubio wrote. “However, any policy seeking to achieve these goals requires basic common sense and an understanding that failure to report troubled students, like Cruz, to law enforcement can have dangerous repercussions.”
The Florida program in question, called Promise, has been successful in reducing disciplinary referrals and student-based arrests in Broward County, where Stoneman Douglas is located.
“The removal of this component, combined with the possibility of armed teachers in our schools, sets the stage for transforming our schools into prisons,” the N.A.A.C.P. said.
Long before the attack in Parkland, Fla., the 2014 discipline guidelines, which encouraged schools to examine their discipline disparities and to take stock of discriminatory policies, were already on Ms. DeVos’s radar — but not because they were seen as a possible culprit in the next school shooting. Conservatives were using the Trump administration’s effort to rein in federal overreach to reverse policies designed to protect against what the Obama administration had seen as discriminatory practices.
In recent months, educators and policy experts from across the country have traveled to Washington to voice support for and opposition to the disciplinary guidance, in private meetings with officials at the Education Department and in a series of public forums.
At a briefing hosted by the United States Commission on Civil Rights, dozens of policy experts, researchers, educators and parents sounded off on the Obama-era discipline policy in a meeting that became so racially charged that some black attendees walked out.
Since the discipline guidelines were issued, conservatives have blamed the document for creating unsafe educational environments by pressuring schools to keep suspension numbers down to meet racial quotas, even if it meant ignoring troubling and criminal behavior. Teachers who sought suspensions or expulsions of minority students were painted as racists, conservatives maintained.
“Evidence is mounting that efforts to fight the school-to-prison pipeline is creating a school climate catastrophe and has if anything put at-risk students at greater risk,” said Max Eden, a senior fellow at the conservative Manhattan Institute, who argued that teacher bias was not the driving force behind school discipline.
But proponents argued that racial bias was well documented.
When the guidance was issued, federal data found that African-American students without disabilities were more than three times as likely as their white peers without disabilities to be expelled or suspended, and that more than 50 percent of students who were involved in school-related arrests or who were referred to law enforcement were Hispanic or African-American.
“Children’s safety also includes protection from oppression and bigotry and injustice,” Daniel J. Losen, director of the Center for Civil Rights Remedies at the University of California at Los Angeles’s Civil Rights Project, wrote in testimony to the Civil Rights Commission. “Fear-mongering and rhetoric that criminalizes youth of color, children from poor families and children with disabilities should not be tolerated.”
The Education and Justice Departments wrote in a 2014 Dear Colleague letter that discipline disparities could be caused by a range of factors, but the statistics in the federal data “are not explained by more frequent or more serious misbehavior by students of color.” The departments also noted that several civil rights investigations had verified that minority students were disciplined more harshly than their white peers for the same infractions.
“In short, racial discrimination in school discipline is a real problem,” the guidance said.
In recent months, Ms. DeVos has said change will be coming. She has already moved to rescind a regulation that protects against racial disparities in special education placements. Her goal, she said last month, was to be “sensitive to all of the parties involved.”
In a bruising interview on “60 Minutes” on Sunday, Ms. DeVos said that the disproportionate discipline issue “comes down to individual kids.” She declined to say whether she believed that black students disciplined more harshly for the same infraction were the victims of institutional racism.
“We’re studying it carefully and are committed to making sure students have opportunity to learn in safe and nurturing environments,” she said.
But Ms. DeVos’s own administration has continued to find racial disparities. In November, the Education Department found that the Loleta Union Elementary School District in California doled out harsher treatment to Native American students than their white peers. For example, a Native American student received a one-day out-of-school suspension for slapping another student on the way to the bus, in what was that student’s first disciplinary referral of the year. A white student received lunch detention for slapping two students on the same day — the student’s fifth and sixth referrals that year.
Broward County was hailed as a leader in the Obama-era discipline reforms, and has trumpeted the district’s crackdown on punitive discipline measures and its large reduction in student arrests.
Its discipline program, Promise, dates back to 2013 — one year before the Obama guidance was issued. Florida’s work in discipline reform dated back to at least 2009, when Charlie Crist, the Republican governor at the time, signed legislation to curb so called zero-tolerance policies.
While Mr. Cruz was repeatedly kicked out of class and ultimately expelled, it is unclear whether he was ever referred to the police for his behavior in school. However, Mr. Cruz was known to law enforcement, which never found cause to arrest him, and a report of troublesome behavior to the F.B.I. went unheeded.
The Broward County superintendent, Robert Runcie, said that Mr. Rubio’s effort to connect the district’s discipline policies to the Stoneman Douglas shooting was misguided.
“We’re not going to dismantle a program that’s been successful in the district because of false information that someone has put out there,” Mr. Runcie said on Twitter. “We will neither manage nor lead by rumors.”