Some spent between $200,000 and $6.5 million to guarantee admissions for their children, FBI Special Agent Joseph Bonavolonta said.
Singer was scheduled to plead guilty in Boston federal court to charges including racketeering, money laundering and obstruction of justice, according to court papers.
The scheme involved getting the children of wealthy people into the colleges of their dreams, often by manipulating sports scholarships, disability allowances on tests, and by inflating resumes.
Among those charged were Oscar nominee Felicity Huffman, Fuller House star Lori Laughlin, and a former tennis coach for the Obamas. She has lately become the queen of the Hallmark Channel with her holiday movies and the series "When Calls the Heart".
The actor supported his wife of more than 20 years on Tuesday at her hearing in an L.A. federal court, where she posted a $250,000 bond.
Loughlin, who was on the cast of the hit 90s sitcom "Full House", is accused of spending $500,000 in bribes to help her two daughters gain admission into USC.
She was among dozens swept up in what prosecutors called the largest college admissions fraud scheme they'd ever seen. Giannulli was released Tuesday after posting a $1 million bond.
Under the guise of a non-profit company that helped students with their college admissions, Singer would pay to have SAT and ACT tests retaken or scores changed, and also for students to be accepted through athletic programs in sports they didn't actually play.
Huffman is accused of making a fake charitable donation of $15,000 "to participate in the college entrance exam cheating scheme on behalf of her eldest daughter", according to prosecutors, who included transcripts of wiretapped conversations between Huffman and a witness in charging documents.
Federal court records unsealed Tuesday in Boston name 50 people, including Huffman and Fuller House actress Lori Loughlin, who have been indicted as part of the alleged nationwide scheme, according to a release from the U.S. Attorney's Office in MA.
Lelling said, via CNN: "This case is about the widening corruption of elite college admissions through the steady application of wealth combined with fraud".
Perhaps most critically, they'll also have to answer for whether qualified students were denied entry into their programs in lieu of the children of the rich and famous. Huffman and Loughlin are among those charged with conspiracy to commit mail fraud and honest services mail fraud. She allegedly discussed doing the same thing for her youngest daughter, though the documents show Huffman didn't go through with it. "They anxious their daughters are as stupid as their mothers", Kellyanne Conway said in a social media post Tuesday.
Macy himself wasn't charged and authorities have not said why.