Boston saw a notable decline in school buses arriving to school on time Thursday — the first day of school — under a new computer model developed by MIT that was supposed to improve efficiencies and on-time performance.
Just 44 percent of buses showed up before the opening bell, down from 51 percent on the first day of school last year.
School officials blamed the delay on too few buses pulling out of the bus yards on time in the morning, even after Superintendent Tommy Chang and Mayor Martin J. Walsh swung by a Dorchester yard to rally the drivers. Less than one-third of the buses left on time, down from 41 percent last year.
“We are working with TransDev, the third-party contractor that employs bus drivers and operates the bus yards, on ensuring that this percentage rapidly improves,” the School Department said in a statement.
Even among the buses that left the bus yards on time, about one-third of them ended up running late.
Earlier in the day, Walsh had complimented the drivers, saying they “were very positive.”
The school system partnered this year with Massachusetts Institute of Technology researchers who developed a new algorithm that aims to help Boston school buses run more efficiently, reducing the number of bus routes from 650 last year to 600 this year while saving the school system about $5 million.
It is a big undertaking: Each morning, Boston school buses are charged with the job of transporting 27,000 students to 230 public, private, and charter schools. The routes, from East Boston to West Roxbury, encompass 1,040 bus stops and 5,136 pickups at individual households where special education students require door-to-door service.
The first day of school is always tricky to use as a litmus test to gauge how buses will run throughout the school year, school and city officials said.
That’s because buses often run behind schedule for the first few days of school as drivers familiarize themselves with the routes and unforeseen obstacles, such as road construction, overlaps with trash collection routes, or parents grabbing photos and exchanging phone numbers with the bus drivers.
“The first day is chaotic,” Walsh said. “You have new routes and new drivers.”
Some schools were hit hard by late buses, as observed by Boston Globe reporters.
At the Josiah Quincy School in Chinatown, more than a dozen buses showed up after the opening bell, including two that were about 45 minutes late, and at Young Achievers K-8 Pilot School in Mattapan, almost half of its buses arrived late.
Earlier in the day Chang attempted to strike a positive note.
“It’s been a smooth opening of the school year,” Chang said during an early morning visit at the Irving Middle School in Roslindale. “I’d like to say the best start of a school year ever.”
Prior to Thursday, at least one independent charter school, KIPP Academy Boston, which started its school year earlier than the Boston system, had problems with buses.
That prompted a parent leader to bring the issue to the attention of the Boston School Committee Wednesday night.
In testimony to the committee, she said a few students had no buses and one bus was overbooked.
“It’s sad [when] you have little ones sitting in school at 7 in the evening,” the mother said.
KIPP did not respond to a request for comment. A Boston school system spokesman said a central office administrator spoke to the parent after the meeting and said “many of the issues mentioned were resolved.”
Once the routes are humming, school officials project that the average commute time for students will be 23 minutes. During the past school year, 88 percent of buses on average arrived to school on time.
Against the backdrop of the transportation changes, parents and students returned to school Thursday with much jubilation. Alex Beaulieu said he was excited about his first day in fourth grade at Josiah Quincy Elementary.
“My favorite part about this year is probably my teacher,” he said. “I got a pretty nice teacher this year, and my friends are in my class.”
Tawanaka Greene, 32, of the South End, who has three children ages 8, 11, and 14 at the Quincy elementary and upper schools, said her house was also buzzing with anticipation Wednesday night.
“They were used to staying up and having TV time, so shutting things down at 7:30 and getting up at 7 in the morning was hard for them,” she said. “They were like, ‘Can we have another hour, please?’ ”Globe correspondent Alyssa Meyers contributed to this report. James Vaznis can be reached at email@example.com. Follow him on Twitter @globevaznis.