Another significant player in the U.S. college-admission scandal has thrown himself on the mercy of the court.

Mark Riddell, a Harvard-educated resident of Florida, has pleaded guilty to two charges in a Boston courtroom. He'll be sentenced at a later date.

According to the indictment, the first count was conspiracy to commit mail fraud and honest services mail fraud; the second was conspiracy to commit money laundering.

They each carry maximum sentences of 20 years in prison.

U.S. prosecutors have alleged that Riddell wrote tests for the children of many wealthy people involved in the scheme, which has ensnared actors Felicity Huffman and Lori Loughlin in legal trouble.

The ringleader, Rick Singer, has pleaded guilty. He's a California-based college-admissions consultant who admitted to hiring Riddell to take tests on behalf of his clients.

Huffman has also pleaded guilty, whereas Loughlin, who has done a fair amount of work in Vancouver, is fighting the charges against her.

There's an allegation from prosecutors that Riddell flew from Tampa to Vancouver on or about December 2, 2011.

Prosecutors have also alleged that Riddell used a "falsified identification card" on or about the following day to secretly take the standardized test for businessman David Sidoo's older son, before flying back to Tampa.

Riddell allegedly flew back to Vancouver on or about June 9, 2012, to take a high school graduation test on behalf of Sidoo's older son before returning to Tampa the following day.

Then in late November 2012, Riddell allegedly flew from Tampa to Los Angeles to take the SAT test for Sidoo's younger son.

None of the allegations involving the Sidoo family has been proven in court.

Sidoo has pleaded not guilty to the same charges that Riddell has been convicted of.

"Mr. Sidoo denies all of the charges," his legal team said earlier this week. "He strongly contests the legal and factual basis for these allegations and will rely on his defense team to defend him in future court proceedings."