A “woeful lack of oversight” and a culture that confused academic freedom with a lack of accountability helped more than 3,100 students at the University of North Carolina at Chapel Hill — many of them athletes — enroll and pass classes they never attended and which were not taught by a single faculty member.

A report released Wednesday by Kenneth Wainstein, a former official with the U.S. Department of Justice, found that the academic fraud was systematic and far-reaching, lasting for nearly 20 years and consisting of 188 classes in the African and Afro-American studies department. About half of the 3,100 students were athletes, and investigators concluded that some university employees were aware of the fraud and actively steered athletes and other struggling students toward the classes.

At least nine employees have been fired or disciplined so far, though Carol Folt, UNC’s chancellor, said the university will not name the employees.

“I know the Carolina community will find these findings sobering,” Folt said during a press conference Wednesday. “This never should have been allowed to happen.”

The report casts an unflattering light on the university, which has long boasted about its ability to balance a proud athletics program with rigorous academics — a perception already bruised by earlier investigations into the fraud. Folt admitted that one of the reasons the fraud went undetected for so long was because many at the university simply assumed that UNC employees were surely above such conduct.

Previously, the university and the National Collegiate Athletic Association had both conducted investigations, but Wainstein’s report revealed the problems were far more pervasive than what was outlined in the earlier investigations. The new report also discusses the problems in the context of athletics, whereas earlier inquiries described a general problem that involved some athletes.

The differing conclusions came about in part because Wainstein was able to interview Julius Nyang’oro, the former chairman of the African and Afro-American studies department, and Deborah Crowder, a retired department administrator.

The Orange County district attorney dropped felony fraud charges against Nyang’oro after he agreed to participate in the investigation. Crowder agreed to talk then as well, though she was never charged. While Nyang’oro, as department chair, turned a blind eye to the academic fraud and later participated in it directly, the report stated, it was Crowder who first created the so-called “paper classes” in 1993.

“She felt that the school paid too much attention to the best and brightest and not enough attention to students who were struggling,” Wainstein said. “She wanted to help students who had difficulties in college.”

According to the report, Crowder identified three groups of students she wanted to help the most: survivors of sexual assault, students with mental health issues, and underprepared athletes. When Nyang’oro became chairman in 1992, she found an ally. Early on in Nyang’oro’s career two of his students, who were athletes, dropped out of college due to low grade-point averages.

One student ended up in prison and the other was murdered.

“Those experiences left him feeling committed to trying to prevent those kinds of tragedies again in the future,” Wainstein said. “So given his hands-off approach and his sympathy with her outlook toward students she considered to be troubled, Crowder took the opportunity to start a line of classes.”

These “paper classes” were designed as independent study courses. The only work required of the students was a research paper, and they were nearly guaranteed an A or a B no matter the quality. Forty percent of the 150 papers analyzed by investigators were at least 25 percent plagiarized, the report stated. These papers generally received A- grades. Later, Crowder created a different type of paper class that was designated as a lecture course. The course appeared in the catalog as having a meeting room and a meeting time, but no students ever met.

No faculty members were involved in the courses, with Crowder signing up students, assigning them their papers, and doing all of the grading. Word of how easy the courses were spread around campus, attracting other types of students — most prominently members of UNC’s fraternities, some of whom took so many courses in the department that they inadvertently minored in African and Afro-American Studies.

The ease of the coursework and the volume of students taking independent study courses raised some red flags with campus administrators, the report stated, but officials were hesitant to act on their suspicions, afraid that they would trample on faculty members’ academic freedom.

“Academic freedom does not mean freedom from accountability,” Folt said, promising increased oversight and reviews of courses, faculty, and chairs. “Instead I believe very strongly that we have to hold each other accountable.”

Other university employees, particularly athletes’ academic advisers, were directly complicit in the continued existence of the courses, the report stated, encouraging students to sign up for the paper classes and even suggesting to Crowder what grades the students needed in order to remain eligible.

As Crowder’s retirement approached in 2009, the advisers grew concerned about what would happen to the athletes’ G.P.A.s. They urged students to turn in their papers before the last day of class, not because that’s how most courses work, but because they would likely receive much lower grades if Crowder was not the one grading them.

“I would expect Ds or Cs at best,” the associate director of the advising program wrote in an email at the time.

The majority of those in the know were academic advisers to men’s basketball and football players, who made up more than half of the athletes taking the courses. But knowledge of the courses was not limited to the marquee men’s programs. As an adviser for women’s basketball players, Jan Boxill, the director of the Parr Center for Ethics and later the faculty chair, steered students to Crowder’s courses with suggestions about what grades they needed, according to emails obtained by investigators.

Even after Crowder’s retirement, the courses continued. Pressured by athletics advisers, Nyang’oro began overseeing the paper classes, raising yet another red flag that was all but ignored by administrators: he was somehow personally teaching more than 300 independent study courses a year. The scheme finally came to an end in 2011 when he stepped down as chair.

More than 20 percent of UNC athletes took the courses during the 18 years they were offered, while just 2 percent of the general student population did. Between 1999 and 2011, about 170 athletes would have seen their semester GPAs drop below a 2.0 at least once if not for the paper classes. When Crowder left in 2009, the football team experienced its lowest cumulative GPA in a decade, a 2.121. Eighty students would not have graduated without the paper classes, though the report does not indicate how many of those were athletes.

It is not yet clear what the university plans to do regarding the grades and degrees that were not properly earned, or if UNC athletics will forfeit any of its wins from the 18-year time period. The university won three NCAA championships during this span. Wainstein’s 136-page report was given to the NCAA, which reopened its own investigation in June and may still bring sanctions against UNC. The NCAA’s original investigation concluded that the university had not violated any NCAA rules, reporting at the time that — as other students also took the courses — there was no indication that athletes received more favorable treatment than non-athletes.

Richard Southall, director of the College Sports Research Institute at the University of South Carolina, said the scandal may be “as big a one that has ever come to light” but that it’s indicative of college sports as a whole.

“The current collegiate model forces fundamentally ‘good’ people to make really poor decisions,” Southall said. “It’s the logical extension of the special admissions that is in place at many universities where players are brought into a system to generate revenue. The players find themselves struggling in this system and will do whatever they need to survive. The advisers find themselves in the same system and so they do whatever they can to get the athletes through it. These are unethical decisions being made, in their minds, ethical because they’re in an unethical system.”

An editorial in The Daily Tar Heel, the student newspaper, argues that the wrongdoing at UNC is an almost inevitable outgrowth of the fundamental tension in big-time college football and men’s basketball, in which athletes who are either academically underprepared or uninterested (or both) and universities as a result compromise themselves to keep them eligible to play.

“The university should look into reforms de-emphasizing the pretense that student-athletes admitted on the basis of their athletic abilities must perform in the classroom at the same pace as students admitted for their academic achievements,” the newspaper said.

Folt said she doesn’t view the report as an indictment of college athletics or of the African and Afro-American studies department, but as illustrating a failure to trust and believe in what all students are capable of achieving.

‘‘I think it’s very clear that this is an academic, an athletic, and a university problem,’’ she said.