The National Labor Review Board on Friday sided with striking school bus drivers and matrons saying the walkout is legal, on the same day that union members lost their health benefits for the first day. NY1's Lindsey Christ filed the following report.

Again and again, the mayor has said he can't make a deal with school bus drivers and monitors because they don't work for him.

"The strike is not against the city," the mayor said Thursday. "It is against the bus companies, and they should be negotiating with them."

But on Friday, the National Labor Relations Board disagreed. The board said the city is, in fact, one of the drivers' primary employers, along with the bus companies.

Even though bus drivers and monitors aren't directly on the city's payroll, the union claimed, and the NLRB agreed, that in many ways, the New York City Department of Education is still their boss because it sets the basic rules drivers work under, such as certification, discipline and seniority.

In fact, that last one is what the strike is all about: whether the city includes seniority protections in its contracts with the bus companies.

"The Department of Education, under the mayor, is firing our people. They hire our people. They discipline our people," Michael Cordiello, president of Amalgamated Transit Union Local 1181, said Thursday. "They are the ultimate employer here. They want to hide behind the fact that they say they're not, but they are."

On Friday, Cordiello said in a statement that he hoped the NLRB decision would finally convince the mayor to come to the table.

"The mayor has the power to put our drivers and matrons back to work as early as Monday," the statement read.

But a DOE spokesperson said its position remains the same.

"This ruling doesn’t change the fact that the union is recklessly holding our students and city hostage over issues it must settle directly with the bus companies," the spokesperson said.

The bus companies said they're stuck in the middle. They plan to appeal the NLRB ruling and, meanwhile, sit down with the union Tuesday, prepared to negotiate through the night to reach a deal. But the union said that without the mayor at the table, there is no deal to be made.