NEW YORK — With the city's biggest school bus driver union set to go on strike Wednesday, education officials have put backup measures in place, and the mayor has sharply criticized the union's plan.

The strike "would necessarily jeopardize the education and safety of the more than 150,000 students who take school buses every single day, in a year when our students have already missed a week or more of school because of Hurricane Sandy," New York City Mayor Michael Bloomberg said in a press conference on Monday. "We have told the unions in unequivocal terms: Do not walk out on our students. A strike would be not only unfair to children and families, it would be totally misguided — because the city cannot legally offer what the unions are demanding."

New York City pays $1.1 billion each year for school busing — an average of $6,900 per student, which officials said is higher than any other school system in the country.

To bring down transportation costs, the city is bidding out contracts for 1,100 school bus routes. The current contracts expire on June 30.

Bloomberg said that the driver union, Local 1181 of the Amalgamated Transit Union, "is demanding that the bids include job protections the city is not legally allowed to provide. During a prior bid attempt, under circumstances that were essentially the same as those this year, the New York State Court of Appeals ruled that the city could not legally include the job protection provision the union is demanding."

In a statement on Monday, New York City Central Labor Council President Vincent Alvarez criticized City Hall for "removing contract language that has been in place for 30 years. ... We need to make sure that only the most experienced and highly skilled workforce is responsible for transporting our most precious cargo day in and day out. At the end of the day, that is what this strike is about.”

With the strike threat looming, the New York City Department of Education (DOE) and other agencies have developed plans to help families get their children to and from school.

School offices will distribute MetroCards to students who use yellow bus service, and reimbursements will be available for families who must drive or use a car service.

The New York City Police Department will add more transit officers and more crossing guards to help manage the anticipated increase in students using public transportation and walking to school. Also, the Taxi and Limousine Commission will issue an alert to all licensees to anticipate increased demand and have the maximum number of cars available.

"The city is prepared to provide those who use yellow bus service with the support they need, and put other resources to use if a strike is called," DOE Chancellor Dennis Walcott said. "Our goal is to make sure students get to school, and to pursue contracts that are safe and more reasonably priced, so that we can direct those savings in the classroom where they belong.”