A California couple became the first parents to plead guilty in the national college admissions scandal, after the U.S. accused them of paying at least $600,000 in bribes to get their daughters into school.

Bruce and Davina Isackson entered their pleas Wednesday in federal court in Boston. They’re among 33 parents charged in the largest case of its kind the U.S. has ever prosecuted. Prosecutors said they schemed to boost their daughters’ entrance exam scores and participated in a second plot to create fake athletic profiles for them to gain admission as recruited athletes.

The Isacksons admitted conspiring with college admissions strategist William Rick Singer, the admitted mastermind of the scheme. From 2015 to February, they plotted to get their two older daughters into prominent California universities and to try to get a third daughter into an elite school as well, prosecutors said.

They will cooperate with an ongoing federal investigation, according to their plea agreements. The government has agreed to write to their sentencing judge seeking leniency if they provide “substantial assistance.”

Of the 33 parents charged in the case, 14 have agreed to plead guilty, while 19 others are challenging the government’s case.

The government has recommended a minimum prison term for Bruce Isackson of 37 months, according to his plea agreement. Davina Isackson faces a lesser term, prosecutors said.

In court Wednesday, Saris said she had concerns about how prosecutors have calculated the possible sentence using federal guidelines.

“There are some thorny issues here. This is not a straightforward case,” the judge said.

The Isacksons, of Hillsborough, are accused of using Singer’s services three times.

In 2016, they hired him to help falsify the college application of their eldest daughter, claiming she was a soccer player and winning her admission to her second choice, the University of California at Los Angeles, prosecutors said. The couple ultimately paid Singer more than $250,000 in Facebook shares for helping her, they said.

The next year, the Isacksons hired Singer to get their second daughter into the University of Southern California, first hiring him to improve her score on the ACT college entrance exam, they said. Singer also sent a falsified sports profile claiming the girl, actually an avid equestrian, was a varsity rower. He allegedly sent it to Donna Heinel, a former senior associate athletic director at USC. Heinel, who has pleaded not guilty, later helped Singer get other students in as recruited athletes even if they didn’t participate in the sports, the U.S. claims.

To reimburse Singer for that effort, Bruce Isackson transferred more than $101,000 in stock to a purported charity Singer operated, prosecutors said, and the couple later transferred almost $250,000 in stock to Singer’s foundation.

Last August, the Isacksons reached out to Singer for their youngest child and were caught on a wiretap talking about making a $100,000 donation to Singer to help her cheat on her entrance exam. Singer was cooperating with the U.S. at this point and claimed in discussions with the couple that he was being audited by the IRS. He secretly recorded a meeting with Bruce Isackson in December.

The government said Isackson feared the IRS might discover the bogus charity, which could result in criminal charges for the couple, and worried it would turn into a “front page story” about “getting these kids into school.” According to an FBI transcript, he spoke of “the embarrassment to everyone in the communities.”

“Oh my God,” he said, according to the transcript. “It would be — yeah. Ugh.”