Actresses Felicity Huffman and Lori Loughlin were among more than four dozen people charged in a nationwide college admissions cheating scandal that involved wealthy individuals purportedly paying up to $6.5 million to place their children into elite universities, say court records released Tuesday.

The alleged scam -- it's said to have placed students in top colleges including Yale, Georgetown, Stanford, University of Southern California, UCLA and the University of Texas -- was run by William Rick Singer of California, who helped parents get their children's college admission through bribes, court documents unsealed in Boston claimed. Officials have been investigating the case, named "Operation Varsity Blues," for more than a year.

Singer, an admissions consulting company founder, pleaded guilty in Boston federal court Tuesday afternoon to charges including racketeering conspiracy and obstruction of justice.

At least 13 people, including Huffman and Loughlin's husband, Mossimo Giannulli, were arrested Tuesday morning and were expected to make their first court appearance later in the day.

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Singer ran the charity, Key Worldwide Foundation, which received $25 million in total to guarantee the admissions, U.S. Attorney Andrew Lelling said during a Tuesday news conference. The charitable foundation was allegedly used as a front to run the admissions scheme.

"This is a case where [the parents] flaunted their wealth, sparing no expense to cheat the system so they could set their children up for success with the best money can buy,” Joseph Bonavolonta, from the FBI's Boston field office, said in a Tuesday news conference.

Most of the students didn't know their admission was due to a bribe, authorities said, but in some cases, the children and their parents took part in the scheme.

"Singer would accommodate what parents wanted to do," Lelling said, adding that it "appears that the schools are not involved."

The scheme allegedly involved extensive coordination with parents. Lelling said Singer had a knack for making fake credentials look realistic enough to avoid inviting close scrutiny.

The children’s parents would allegedly pay a specified amount of money, fully aware it would be used to gain college admission. The money would then go toward an SAT or ACT administrator or a college athletic coach, who would fake a profile for the prospective student — regardless of ability, according to the charging documents.

"There can be no separate college admission system for the wealthy and there will not be a separate criminal justice system either," Lelling said. "We're not talking about donating a building so a school is more likely to take your son or daughter, we're talking about deception or fraud."

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On a call with one parent, prosecutors said, Singer described the business simply: “What we do is help the wealthiest families in the U.S. get their kids into school. ... My families want a guarantee.”

Singer would help his clients' children by having another individual take SAT or ACT tests on the youngsters' behalf, officials said. Parents would allegedly pay up to $75,000 for each test and wire money to "charitable accounts." He would purportedly discuss with his clients what SAT or ACT score was desired, aiming for something impressive but not overly so. He would then instruct Mark Riddell, of Florida, to take the exams for the students, or "replace the students' exam responses with his own." Riddell had been working with Singer since 2011, documents stated.

"Singer used the purported charitable donations from parents, at least in part, to bribe two SAT and ACT test administrators," court documents stated.

Some parents would allegedly take their children to therapists paid by Singer in order to receive notes saying they needed extra time to take standardized tests.

Among the college coaches involved in the alleged scheme was Rudy Meredith, the former head women's soccer coach at Yale, and John Vandemoer, the sailing coach at Stanford University. Vandemoer has been fired from his position, the university said in a statement Tuesday.

Singer would allegedly bribe the coaches to fill slots the universities allocated for new players with his clients' children. To evade suspicion, the coaches and Singer would allegedly tell the prospective students to pose for pictures or would alter stock images and Photoshop their faces onto athletes' bodies, to support athletics-based admissions.

For one applicant, Meredith — who resigned from his position in November — created a fake athletic profile and said the person was a recruit for the Yale women's soccer team even though the applicant "did not play competitive soccer," officials said. Singer allegedly gave Meredith $400,000 after the student was admitted to Yale.

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A Georgetown tennis coach received bribes between 2012 and 2018 from Singer that amounted to more than $2.7 million, according to the documents.

"In exchange for the bribes, the Georgetown coach designated approximately 12 applicants as recruits for the Georgetown tennis team, including some who did not play tennis competitively, thereby facilitating their admission to the university," documents read.

Some of the "student-athletes" who were enrolled reportedly never showed up for practice, while others pretended to be injured. Some played briefly, then quit, Lelling said.

Huffman and her husband, actor William H. Macy, were accused of taking advantage of the SAT and ACT. Macy was not among those charged Tuesday.

The two parents allegedly helped their daughter with her college admission by making a “purported charitable contribution of $15,000 ... to participate in the college entrance exam cheating scheme,” the documents said. “Huffman later made arrangements to pursue the scheme a second time, for her younger daughter, before deciding not to do so."

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In a January interview with Parade, Macy discussed how "stressful" applying to colleges had been.

“She’s going to go to college. … We’re right now in the thick of college application time, which is so stressful,” Macy said. “I am voting that once she gets accepted, she maybe takes a year off. God doesn’t let you be 18 twice. … But it’s just my opinion, and we’ll see what she wants to do, what Felicity thinks and how the chips fall.”

The court documents also stated that "[Loughlin and her husband, fashion designer Mossimo Giannulli] agreed to pay bribes totaling $500,000 in exchange for having their two daughters designated as recruits to the USC crew team -- despite the fact that they did not participate in crew -- thereby facilitating their admission to USC."

Lelling said the case is still an active investigation and there could be more parents and coaches involved. The vast majority of the children accepted as part of the alleged admissions scheme are reportedly still enrolled and are active students.

Several colleges, including Yale, University of Texas and USC, released statements following Tuesday's news conference saying they were "victims" of the bribery scheme.

"As the indictment makes clear, the Department of Justice believes that Yale has been the victim of a crime perpetrated by its former women’s soccer coach. The university has cooperated fully in the investigation and will continue to cooperate as the case moves forward," Yale University spokesman Tom Conroy said in a statement.

USC said it will be conducting its own internal investigation and "identifying any funds received by the university in connection with this alleged scheme."

Stanford said in its statement: "The charges state that sailing head coach John Vandemoer accepted financial contributions to the sailing program from an intermediary in exchange for agreeing to recommend two prospective students for admission to Stanford. Neither student came to Stanford. However, the alleged behavior runs completely counter to Stanford’s values...Based on the Department of Justice investigation to date, we have no evidence that the alleged conduct involves anyone else at Stanford or is associated with any other team. However, we will be undertaking an internal review to confirm that."

The College Board also released a statement following the arrests, vowing to always take the "necessary steps to ensure a level playing field for the overwhelming majority of test takers who are honest and play by the rules."

“Today’s arrests resulting from an investigation conducted by the U.S. Attorney’s Office in Massachusetts send a clear message that those who facilitate cheating on the SAT – regardless of their income or status – will be held accountable," the statement said. "The College Board has a comprehensive, robust approach to combat cheating, and we work closely with law enforcement as part of those efforts."