As more and more schools adopt computer-based digital learning, the risk of cyberattacks on schools grows.

Recently a school in Avon, Connecticut, was targeted by hackers.

AVON, Conn. — Over six weeks, the vandals kept coming, knocking the school system’s network offline several times a day.

There was no breach of sensitive data files, but the attacks in which somebody deliberately overwhelmed the Avon Public Schools system in Connecticut still proved costly. Classroom lesson plans built around access to the internet had come to a halt.

“The first time I called the FBI, their first question was, ‘Well, what did it cost you?’” said Robert Vojtek, the district’s technology director. “It’s like, ‘Well, we were down for three-quarters of a day, we have 4,000 students, we have almost 500 adults, and teaching and learning stopped for an entire day.’ So how do you put a price tag on that?”

The kind of attacks more commonly reserved for banks and other institutions holding sensitive data are increasingly targeting school systems around the country. The widespread adoption of education technology, which generates data that officials say can make schools more of a target for hackers, also worsens an attack’s effects when instructional tools are rendered useless by internet outages.

Schools are attractive targets because they hold sensitive data and provide critical public services, according to the FBI, which said in a written statement that perpetrators include criminals motivated by profit, juvenile pranksters and possibly foreign governments. Attacks against schools have become common, the FBI said, but it is impossible to know how frequently they occur because many go unreported to law enforcement when data is not compromised.

Attacks often have forced districts to pull the plug on smart boards, student laptops and other internet-powered tools.

Schools in the Florida Keys took themselves offline for several days last September after a district employee discovered a malware attack. Monroe County schools Superintendent Mark Porter said teachers had to do things differently but adapted quickly…

The 2,000-student Coventry Local School District in Ohio had to close schools in May as staff worked to fight a virus of that had infected the network. The FBI helped to guide the district through the recovery and offered assistance on best practices…

In North Dakota, where a third of schools statewide were hit with a malware attack last year, it was traced to North Korea, although it’s unclear if that country was the origin of the attack or just the location of a device that was used as a stepping stone, according to Sean Wiese, the state’s chief information security officer.