A two-year corruption investigation into the Detroit Public Schools led to federal charges Tuesday for a dozen current and former principals who stand accused of stealing nearly $1 million in a bribery-and-kickback scheme based on the school system’s procurement of school supplies from an outside vendor. The Detroit Public School System is the largest in the cash-strapped state and needed emergency-funding legislation signed on Tuesday by the governor to keep the schools open through the end of the school year.

Here’s the crux of the corruption scheme from the Associated Press:

Fraudulent invoices were submitted for chairs, paper and other supplies. Some supplies were never delivered, and in other cases, the quantity of supplies delivered was less than ordered. The vendor, Allstate Sales, received $2.7 million from the cash-strapped district, while the school officials, who apparently didn’t know others were involved in the scheme, received kickbacks of more than $900,000 in cash, gift cards and checks.

“The news of the corruption case at a critical time as the state grapples with fixing the finances of the struggling Detroit district, the largest school system in Michigan. DPS has been under the control of a state-appointed emergency manager since 2009 and has accumulated an operating deficit of $515 million,” the Detroit Free Press reports. “Just last week, the Legislature passed $48.7 million in emergency funding to ensure that DPS doesn’t run out of cash early next month, as well as put the district under the authority of a financial review commission to oversee the district’s finances.”