Martin Fox entered the plea in Boston's federal court Friday.
The 62-year-old from Houston had previously agreed to plead guilty to a racketeering conspiracy charge in a deal with prosecutors.
Authorities say Fox brokered bribes to help wealthy parents rig their children's college entrance exams.
He was also accused of arranging bribes to get two students admitted to the University of San Diego as recruited athletes, and one to the University of Texas.
He has agreed to forfeit $245,000 received through the scheme.
His charge carries a sentence of as many as 20 years in prison, but prosecutors are recommending a punishment at the low end of guidelines.
His sentencing is scheduled for Feb. 14.
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