Close to 150,000 New York City students could lose school bus service next month if operators follow through on a threat to yank drivers off the job over a bitter contract impasse , according to a formal warning filed Monday.

The private school bus companies notified the state Labor Department that, if a citywide education panel does not approve their contract extension, they would be forced to lay off 12,000 unionized drivers and attendants at the end of the business day on Oct. 31.

Absent a long-term agreement, the bus vendors have been operating on emergency extensions, and the Panel for Educational Policy was planning to take the latest extension up in November. Members have been doing so every two months since the last renewal expired over the summer.

“Their threat to withho

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