Boston Public Schools students are returning to their classrooms after summer break, but for some the journey this year has been bumpier than usual.

Last week, as many charter school students went back to school, some school bus routes were delayed by up to two hours.

The company that BPS contracts with on transportation, Transdev, is currently in negotiations with the bus drivers union, and the threat of a strike looms in the background. The buses have been operating without a contract since last Friday.

Paul Reville, professor at the Harvard Graduate School of Education and former state secretary of education, weighed in on Boston Public Radio.

"I think there was a commitment in the new administration in the interim to focus on operational issues. Apparently a labor action has gotten in the way to some degree. It's hard to figure out from the facts that we have who is at fault here," Reville said.

Reville said that, regardless of where the blame lies, the delays don't inspire confidence in the system for BPS families.

"From a parent's standpoint or ... from a student's standpoint, we don't appear as a system to be ready to go," he said. "That's a really poor message to be sending at the beginning of the year."