A ruling from the National Labor Relations Board found in favor of the striking bus drivers and escorts, arguing that the labor action was legal because the union was engaged in a dispute with its “primary” employers who the NLRB defined as both the bus companies and the city’s Department of Education.

The short-term result: the strike by Local 1181 of the Amalgamated Transit Union grinds on. In the longer term, the bus companies say they will appeal the ruling.

“We are disappointed but not surprised at the ruling,” said Jeffrey Pollack, chief labor attorney for the bus contractors’ coalition. “The bus companies will continue to do everything we can to get the buses rolling so we can get New York City’s school children back to school safely. We believe the NLRB’s decision is incorrect and plan an immediate appeal.”

At the heart of the NLRB ruling was this sentence: “It is well established that more than one employer may be a primary employer.” Both the city and the bus companies have been tossing the responsibility for the strike back and forth like a hot potato but the ruling suggests they share the title of employer in this case, and therefore must both be involved in a resolution.

According to a Department of Education statement, the city did not see it that way.

“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,” said D.O.E. spokesperson Erin Hughes.

The ruling also rejects the companies’ position that the dispute was between the workers and the city because it focused on the city’s issuing bids for new bus contracts without Employee Protection Provisions, or EPPs.

The city said a Court of Appeals ruling made it illegal to include the EPPs in the contract bids.

Meanwhile, the D.O.E. reported about 2,949 bus routes were running as of Friday morning, out of a total of 7700. That is 89 more routes than Thursday, making it the biggest one-day increase since the strike began on Jan. 16.