Just days after responding to the city’s school bus crisis by firing a top official and reassigning another, schools Chancellor Richard Carranza put his staff on notice that when things go wrong they better act quickly — or he will find someone who will.

“When things don’t go right I expect a sense of urgency to serve our community,” Carranza said in an interview with Chalkbeat Monday. “And if we can’t make it happen, then we’ll make sure that there are people in place that will make it happen. It’s really that simple.”

Problems with the city’s school bus services are not unusual, especially at the start of the school year. But since the start of classes, the city’s school transportation hotline has seen a 17 percent increase in calls over the same period last year. And revelations about drivers who were not properly vetted, buses arriving late, students trapped on hours-long routes crisscrossing the city, or buses simply not arriving at all have dominated the opening weeks of Carranza’s first full school year, splashing across the front page of the Daily News.

Last week, after deeming the situation “unacceptable,” Carranza fired Eric Goldstein, the CEO of school support services responsible for transportation, school food, and the public school sports league. Carranza also reassigned Elizabeth Rose, who had been CEO of school operations and a top deputy under former Chancellor Carmen Fariña, to focus solely on transportation contracts.

Carranza said Monday that a broader shakeup to the $1.2 billion-per-year bus system, which serves roughly 150,000 students, two-thirds of whom have disabilities, could be coming.

“As we understand more fully how [the Office of Pupil Transportation] in particular operates, I wouldn’t be surprised if there aren’t some more changes,” he said. Leading that effort will be Kevin Moran, a former borough field support director who will now serve as a senior advisor to Carranza on transportation — while the city searches for a permanent leader.

The busing problems are the first significant test of Carranza’s leadership during a crisis since taking the helm of the nation’s largest school system last April. So far, Carranza’s response has echoed his reaction to much larger issues such as school segregation — that he’s interested in systemic fixes and doesn’t want to excuse the issue just because it has bedeviled past chancellors. Under changes made by Carranza’s administration, school bus drivers will undergo the same background checks and have investigations handled by the same education department unit as other schools staffers.

But so far, his response to the crisis has drawn mixed reactions from some advocates, observers, and education department insiders.

Maggie Moroff, a disability policy expert at Advocates for Children, said busing issues often linger through much of the school year. In the past, the education department has reacted defensively, fixing bus issues in individual cases when advocacy groups get involved but rarely pledging to overhaul the system, she said.

“We get a lot of students at this time of year who have not been to school yet because they don’t have a bus,” Moroff said. “It’s exciting to hear the chancellor say, ‘it’s unacceptable and we’re going to do something about it.’”

But overhauling the bus system will be a massive undertaking, partly owing to the technical complexity of ferrying students to schools with different schedules, shifting rosters of students necessitating new routes — but also because the system is dependent on a rough-and-tumble web of private bus companies. (Goldstein, the support services CEO who Carranza fired, reportedly faced down the CEO of a bus company who confronted him with a loaded pistol during contract negotiations in 2010.)

Eric Nadelstern, a top education department deputy during the Bloomberg administration, said Carranza may be underestimating the bus system’s complexity and the value of keeping leaders with deep knowledge of it.

“Goldstein at the very least understood where the pitfalls were,” Nadelstern said, adding that removing a leader in the middle of a crisis may prove unwise. “I don’t think there’s anyone else in the system who has that knowledge or capacity.”

The Bloomberg administration attempted an overhaul of the bus system in 2007, hiring private consultants in an attempt to make it more efficient. That effort turned out to be a flop, the New York Times reported, “leaving shivering students waiting for buses in the cold and thousands of parents hollering about disrupted routines.” Klein eventually apologized but largely defended the reorganization at the time, saying, “I never think that the pain is worth it. On the other hand, I don’t think there’s any good time to make these changes.”

Others, including one current education department administrator who spoke on condition of anonymity, said they worried that Carranza wanted to show he was taking charge of the situation by making heads roll without immediately addressing the underlying problems.

But while Carranza admitted he does not yet have a full explanation of why the school bus system has repeatedly fallen short, he said he is committed to a longer-term solution.

“My understanding is this goes back at least decades,” Carranza told Chalkbeat. “There are some systemic issues that I don’t want to put a band-aid on, I want to actually find the root cause and fix.”