Fewer than half of Indianapolis Public Schools students showed up to school on Friday after the district was forced to cancel bus service because too many bus drivers called in sick, officials said.

The district canceled all bus service after 95 of the district’s roughly 550 drivers and monitors said they could not come to work, according to IPS Superintendent Aleesia Johnson. The driver shortage came about a month after the school board approved a controversial plan to outsource all of its transportation.

The union representing bus personnel, however, said it did not support or organize Friday’s sick-out.

“We strongly condemn the actions of these rogue employees who chose to make this decision, despite the guidance of their union leadership to not move forward with these actions,” Johnson said at a press conference Friday. “Their lack of concern for the safety of students in elementary through high school in the middle of winter is disappointing.”

The district buses about 22,000 students each day.

Schools remained open Friday, but with only about 14,000 of the district’s 31,800 students reporting to school, those who did not show up were not marked as absent.

District officials are talking with leaders from the union, AFSCME, to ensure that drivers show up for work on Monday, said Johnson.

David Robertson, executive director of AFSCME Council 962, said drivers were not demonstrating as part of an organized union action. In a written statement, the union said that “the leaders of our affected locals assured us that there was no union endorsed effort to disrupt operations.”

The union statement acknowledged that many of its members have been disappointed with the district’s decision to contract out routes. As a result, “some employees may be acting independently based on these feelings,” it said. “However, two wrongs don’t make a right.”

Last month, the Indianapolis Public Schools board approved a contract with a new outside transportation provider, First Student, which is expected to replace the current combination of buses run by a contractor, Durham, and district-managed buses. District officials said that outsourcing would save Indianapolis Public Schools about $7 million annually. Current drivers will need to reapply for jobs with First Student. The new contract goes into effect on July 1.

At a school board meeting before the board approved the contract, dozens of bus drivers and union members turned out to oppose the change and plead with district leaders not to outsource transportation.

The outsourcing decision is part of a broader IPS push to reduce spending in non-academic areas. The district embraced the approach two years ago in order to garner support from the Indy Chamber for a tax increase to pay for higher teacher salaries.