Cheating is not just for students, according to the results of a recently concluded federal investigation into a long-running scheme to subvert the results of a teacher licensing exam. Yahoo News reports that for a decade and a half, candidate teachers paid Clarence Mumford, Sr. to send ringers to take their Praxis exam. They paid him between $1,500 and $3,000 for each attempt.

According to federal prosecutors in Memphis, Tennessee, the end result was that as many as hundreds of thousands of students in public schools around the South were being taught by teachers who weren’t qualified to hold their jobs.

Now, Mumford stands accused of more than 60 charges of fraud and conspiracy stemming from the creation of fake IDs to allow those hired to take exams to impersonate the real candidates.

The hired-test takers went to testing centers, showed the proctor the fake license, and passed the certification exam, prosecutors say. Then, the aspiring teacher used the test score to secure a job with a public school district, the indictment alleges. Fourteen people have been charged with mail and Social Security fraud, and four people have pleaded guilty to charges associated with the scheme. Mumford “obtained tens of thousands of dollars” during the alleged conspiracy, which prosecutors say lasted from 1995 to 2010 in Arkansas, Mississippi and Tennessee.

Among those implicated in the scheme were former NFL wide receiver Cedrick Wilson, who is accused of going through Mumford to have the Praxis physical education exam taken for him. Although Wilson is currently out on a $10,000 bond and awaiting trial on four charges of Social Security and mail fraud, he has been suspended from his position in the Memphis City Schools.

To make his test-taking system a success, Mumford relied on his experience working in the Memphis Public Schools. He knew that on the days the test was administered, proctors didn’t take care with ID checks and didn’t employ any measures to determine if the identification they were presented was counterfeit. Exam registration and payment of the test fee all took place over the internet, meaning that teacher candidates never even needed to travel to the test site or meet with Mumford for the deception scheme to be successful.

Since the investigation came to light, Mumford has lost his position at Memphis Public Schools, and many of the ones he’s accused of helping – like Wilson – have been suspended. Yet according to Yahoo, at least three of the teachers accused of making use of Mumford’s services remain employed.

The uncovered scandal highlights the relative fragility of the system designed to determine who is and who is not qualified to front a classroom.

“As technology keeps advancing, there are more and more ways to cheat on tests of this kind,” said Neal Kingston, director of the Center for Educational Testing and Evaluation at the University of Kansas. “There’s a never-ending war between those who try to maintain standards and those who are looking out for their own interests.”