A longtime Memphis educator accused of leading a 15-year scheme to help teachers cheat on qualification exams changed his plea to guilty on Friday, a week after he rejected a deal from prosecutors.

Clarence Mumford Sr., 59, agreed to plead guilty to one count of conspiracy to commit mail, wire, identification and Social Security fraud and one charge of aggravated identity theft. Prosecutors said the two counts can carry seven years in prison when Mumford is sentenced May 13.

Prosecutors say teachers in Tennessee, Mississippi and Arkansas paid Mumford $1,500 to more than $3,000 to have ringers take the Praxis certification tests for them. That fee included fake driver's licenses Mumford made for the test-takers, who showed them to proctors at examination centers.

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The passing test scores were then used to help people get jobs in public schools. 

On Jan 25, Mumford told U.S. District Judge John Fowlkes that he wanted to go to trial on more than 60 fraud and conspiracy charges. Defense lawyer Coleman Garrett said Mumford told him at the time that that he was "all prayed up" and a higher power was going to help him at trial.

The deal Mumford rejected last week called for between nine and 11 years in prison in return for his guilty plea.

His attorney, Coleman Garrett, said the lower possible sentence was a reason why Mumford chose to accept a new plea deal.

"Maybe that higher power that he was talking about works," Garrett said.

Mumford was a former guidance counselor and assistant principal in the Memphis City Schools system. Authorities say he paid ringers $200 to $800 to take tests in social studies, history, school guidance counseling and physical education. The stand-ins passed many of the tests they took, but they also failed some.

Authorities say his scheme ran from 1995 to 2010, and affected hundreds, if not thousands, of public school students who ended up being taught by instructors who never qualified for their positions. After they were indicted, some teachers were fired or suspended, while others remained employed by their school systems. One became a school principal in Mississippi.

Prosecutor John Fabian showed the judge pictures of the fake licenses Mumford made, and correspondence between Mumford and the teachers. Mumford used his credit card to pay for test registrations and even included his cellphone number on test applications, Fabian said.

Teachers were charged with fraud for giving Mumford their Social Security numbers and other identification information so that he could make the fake licenses. Six teachers and test-takers already have pleaded guilty, and five other teachers have indicated they plan to. Prosecutors say 18 other people have agreed to court-ordered diversion in the case.

Educational Testing Services, which writes and administers the Praxis examinations, has said the company discovered the cheating in June 2009, conducted an investigation and canceled scores. The company began meeting with authorities to turn over the information later that year.

Mumford told the judge that he suffers from high blood pressure and diabetes. Garrett said at the hearing last week that Mumford could die in jail if convicted on all counts at trial.