NEW ORLEANS (AP) — The school bus company that transports most public school students in New Orleans has laid off its drivers in a dispute over $7.2 million in unpaid bills.

Blaine Krage, a spokesman for Warrenville, Ill.-based Durham School Services, told The Times-Picayune Tuesday that the company has sent termination letters to 142 drivers and 55 bus monitors telling them “we will not need their services this upcoming school year.”

Krage said the Recovery School District owes Druham $7.2 million, or more than half the value of its one-year contract, which ended June 30. Some of the charges date back to 2011, he said.

Durham will not negotiate a school bus contract for the 2012-13 school year, which begins in about a month, until the back pay issue is settled, Krage said. Durham’s drivers have been paid their wages and are not owed any money in the dispute with the RSD, he noted.

The reason for the unpaid bill was not immediately clear. Krage said the debt amount is not in dispute.

Officials with the RSD were not immediately available for comment.

Durham also provides service for a smaller number of students attending schools under the Orleans Parish School Board, but those students apparently aren’t affected by the layoffs.

Durham is a national company that provides local school transportation services. It has transported children to Recovery School District schools for the past two years.