They're back to their dirty old tricks.

The city's Department of Education has continued to privatize the cleaning of dozens of its public schools through no-bid contracts -- despite a 2004 court order forbidding the practice, a lawsuit charges.

The DOE once again violated competitive-bidding rules by handing over tens of millions of dollars in custodial contracts to the cleaning agency Temco Service Industries, charges Robert Troeller, president of the International Union of Operating Engineers Local 891.

The DOE lost a similar battle seven years ago when a state Supreme Court justice nullified $60 million worth of contracts with Temco and Johnson Controls because of a failure to bid out the deals.