THE BRONX - Students headed back to school this morning, despite a looming school bus strike that could potentially strand 150,000 kids citywide.

The bus drivers' union, Local 118, is threatening to walk off the job unless it gets seniority rights guaranteed in its new contract. Officials say there is a contingency plan in place, but it relies mostly on public transportation and parents.

The Department of Education says it will issue MetroCards to students who rely on yellow bus service, as well as to parents of special-needs children in kindergarten through second grade.

Mayor Michael Bloomberg called the possible strike illegal, and the city has taken legal steps to try and prevent it. Meanwhile, the union has not indicated when it could start to picket.

For video of Mayor Bloomberg's speech on the potential bus strike, select iO Extra on Channel 612.

DOE yellow bus service information for parentsMayor Bloomberg's release ahead of bus strikeChancellor Wallcott's letter to parents