In addition, a DPS vendor -- identified as Norman Shy, 74, owner of Allstate Sales -- was charged. He is accused of being at the center of the criminal activity.  Shy would submit fraudulent invoices for school supplies, according to U.S. Attorney for the Eastern District of Michigan Barbara McQuade. The principals involved would approve those invoices and then Shy would provide some, but not all, of the goods he promised to sell, she said.  Shy allegedly paid the principals a total of $900,000 for their trouble. In exchange, he received payments from the school system for $5 million, of which officials believe $2.7 million was fraudulent.  The bribery is said to have stared in 2002 and continued until January 2015.  "The real victims in a case like this, of course, are the students and the families who attend Detroit Public Schools -- the teachers, the educators who really want to make a difference in the lives of Detroit Public School children," McQuade told reporters. "A case like this is a real punch in the gut for those who are trying to do the right thing."  Of the 13 Detroit Public School officials charged, seven are former school principals; six are still working in that capacity. One of the former principals is now an assistant superintendent.  Included among those implicated is the principal of Spain Elementary-Middle School. His involvement is notable because the school was recently tapped by Ellen DeGeneres to receive half a million dollars in donations, after  that the Lowe's chain of home-improvement stores would donate $500,000 toward repairing the school, including $50,000 in new computers and a $100 Visa gift card to every teacher and staff member.  "I wanted to surprise you," DeGeneres told the school's community in a video posted online. "I love your school, I love what you stand for."  McQuade recognized during her news conference that accusations of public corruption never come at a good time. Still, it's coming at a particularly bad time for Detroit Public Schools.  The school system is hundreds of millions of dollars in debt, and being sued by the union.  Just this month, there were threats of a sickout.  , a sickout is a way for teachers to protest working conditions, dilapidated facilities and inadequate funding.  Embattled Gov. Rick Snyder, who is also dealing with the fallout from the Flint water crisis, said in his State of the State address that the city's schools are in a crisis.  The school system was previously under the supervision of an emergency manager appointed by Snyder, Darnell Earley.  Earley, who was also Flint's emergency manager from 2013 to 2015,  McQuade said Tuesday that if there is a message to be taken from the kickback case, she hopes it will be one of accountability.  "It may seem easy to take a bribe but, I'll tell you what, it's also easy to get caught," she said. "And we will catch you."  CNN's Joshua Berlinger and journalist Remi Merhi contributed to this report.
Thirteen current or former principals with the Detroit Public Schools were charged with bribery Tuesday in an alleged kickback scheme.