Among the impacted systems were the school district’s student information system, which has personal data, academic records and schedules, and a transportation system that provides real-time information about school bus routes.
Dr. Torres-Rodriguez, the Hartford schools superintendent, said that the student information system had been fully restored by midnight on Tuesday, after a seven-hour rebooting process. But at around 4:30 a.m., the transportation system had not yet been fully repaired.
Though most of Hartford’s students had opted for remote education, a significant number were still expected to attend in-person classes on Tuesday. Concerned that those students would not have safe transportation, the superintendent decided to cancel school, she said.
“If we know that we have nearly 4,000 students that are expecting to come to school, relying on bus transportation, than we have to make sure that we make that available,’’ Dr. Torres-Rodriguez said.
Officials hoped to have the school district’s information systems fully restored on Tuesday, Mr. Bronin, the mayor, said. But employees were also going “school to school, desktop to desktop” to make sure that teachers’ equipment was not affected and could be safely used for in-person and remote instruction.
Mr. Bronin said officials were not sure who was behind the attack or whether it was intended to target the first day of school. The Hartford police chief, Jason Thody, said officers were investigating and had sought assistance from the F.B.I.
School districts across the United States have increasingly been targeted by hacks and cyberattacks. Last week, the public school system in Miami-Dade County, Fla., was hit with multiple cyberattacks on the first day of school. A 16-year-old student was later arrested and charged in connection with them.