(CNN) - Three more parents, including one CEO who has written books on parenting, pleaded guilty to charges stemming from the college admission scandal in federal court in Boston on Friday.
Jane Buckingham, Robert Flaxman, and Marjorie Klapper all pleaded guilty to one count of conspiracy to commit mail fraud and honest services mail fraud.
And much like three other parents who pleaded guilty on Wednesday, Buckingham, Flaxman and Klapper all admitted to securing the services of William "Rick" Singer, the mastermind of the plot, but not knowing how the plot worked.
"It was all through Mr. Singer," Buckingham told the judge. "I didn't know who was involved."
Prosecutors said they had evidence, which included recorded phone calls and emails showing them working out the details directly with Singer.
Prosecutors said Buckingham, a California resident and CEO of a boutique marketing company, asked Singer if she could get a copy of the exam so her son, who could not travel due to fragile health, could take the test at home, prosecutors said. Meanwhile, test-taking guru Mark Riddell was at a Houston outpost taking the exam for Buckingham's son, according to prosecutors.
Buckingham, whose books include "The Modern Girl's Guide to Sticky Situations," even provided Singer with a sample of her son's handwriting so that Riddell could fake it on the exam, prosecutors said.
Riddell took the ACT for her son in July 2018 and scored 35 of 36, prosecutors said. Buckingham paid $50,000 to Singer's sham charity, the Key Worldwide Fund, prosecutors said.
Marjorie Klapper exchanged emails with Singer about getting extra time on the ACT and SAT exams for her son in 2017. As part of the scheme -- her son took the ACT exam at the West Hollywood Test Center where Riddell served as the proctor.
Klapper's son received a score of 30 out of possible 36 according to the complaint.
Klapper paid Singer $15,000 in November 2017, prosecutors said.
Flaxman, the president and CEO of a Los Angeles-based real estate development firm, arranged through Singer to get his son admitted to the University of San Diego, prosecutors said.
Flaxman also arranged for his daughter's ACT exam to be proctored by Riddell,
Flaxman paid Singer $250,000 for his son's admission to the school and $75,000 for his daughter's inflated test scores, prosecutors said.
The three are slated to be sentenced in October.