After pressure from progressive groups, the head of student loans at the Education Department (ED) resigned from his position on Friday.

Mark Brown, who was the chief operating officer at ED's office of Federal Student Aid, oversaw a trillion-dollar student loan portfolio — making it equivalent to the nation's fifth-largest bank. He was appointed by former Education Secretary Betsy DeVos, after the resignation of his predecessor, A. Wayne Johnson.

Robin Minor, currently the deputy COO for Partner Participation and Oversight, will serve as interim COO.

Pressure for Brown to resign had been mounting, with progressives from Sen. Elizabeth Warren (D-MA) to advocacy groups such as the Americans for Financial Reform pushing for Brown to leave.

The resignation was announced by the newly-confirmed Secretary of Education, Miguel Cardona. Advocates are now pressing for an old student loan hand to fill the position.

“I accepted the resignation of Federal Student Aid Chief Operating Officer Gen. Mark Brown and thanked him for his service to the U.S. Department of Education," Cardona said in a statement. "As the nation continues grappling with economic disruptions caused by the COVID-19 pandemic, the need to deliver relief and fortify pathways to the middle class is more urgent than ever."

The office of FSA was "designed in an unusual way," Jason Delisle at the American Enterprise Institute, told Yahoo Finance.

"When this position was created, it was done so to try to attract people from the private sector... and that would insulate them from politics," Delisle explained. But "what you have [here] is essentially him resigning but you also have people exerting, ironically, political pressure to oust him."

Warren, one of Brown's critics, applauded the his resignation, calling it "good for American borrowers."

"Students deserve leadership at this office who will follow the law and make this program work for students and I look forward to working with Secretary Cardona to reform the FSA so that it works for student borrowers instead of big student loan servicing corporations," Warren said in a statement.

Two names that are being floated as replacements are Mark Kaufman, who was a former banking regulator in the state of Maryland, and Abigail Seldin, according to Huffpost. While Seldin has been criticized by some progressives for working with Educational Credit Management Corporation, a private student loan guaranty agency, when it bought her company College Abacus, many others have come to her defense as a champion of students' needs and rights.