HAVERHILL (CBS) — Haverhill canceled school Thursday after the district’s computer system was hit in a ransomware attack.

Second, third and fourth graders were scheduled to return to full in-person learning, but some parents and students didn’t get the message and showed up at the Tilton elementary school only to find it was closed for the day.

The attack affected all schools in town from pre-K through high school. The day will be treated like a snow day and will be made up at the end of the school year.

According to Haverhill Superintendent Margaret Marotta, the district’s IT department was able to shut down the system Wednesday before there was large-scale corruption.

“Given that it was to be the first day back to school for grades 2, 3 and 4 we do feel confident that we will be able to offer the level of information and communication needed to welcome hundreds of students back to new teachers and classrooms,” Marotta said in an email to parents and staff Wednesday.

The shutdown affected the entire computer network, including email, Schoolbrains, Google and Google Meet as well as the schools’ phone systems.

“We know this is heartbreaking for many that were looking forward to a return to something near normal, and we are hopeful that school will resume on Friday, but we are not able to confirm whether or not school will be in session on Friday at this time,” Marotta said.