Some Detroit principals who faced bankruptcies, tax liens and other financial troubles are accused of taking kickbacks on inflated invoices for classroom supplies in a school system already crippled by debt.

The educators are the latest focus of federal authorities trying to wipe out a culture of corruption that has entangled city public servants.

A public records search by The Associated Press reveals that at least seven of those charged last month in the kickback scheme had troubled personal finances around the same time that a district vendor started doling out an estimated $900,000.

His company received about $2.7 million over 13 years from the district, which was in danger of running out of money until the state stepped in with funding.

The U.S. Attorney's Office says 11 guilty plea deals are scheduled starting Thursday.