PHOENIX » Three Arizona high school students who were on the verge of flunking their classes have been arrested after officials said they hacked into their teachers’ computers and improved their grades.

Police say the Prescott High School juniors attached a device to the computers of several teachers that secretly recorded keystrokes to capture their usernames and passwords. They then bumped up their grades, but a teacher eventually became suspicious after noticing that a student’s listed grade wasn’t consistent with his efforts in class.

"They were definitely low grades and close to failing," Lt. Ken Morley said.

The three 16-year-old boys face juvenile proceedings on charges of tampering with public records and computer tampering, police said Thursday.

Morley said the first student police talked to implicated the other two during questioning.

"We talked to the first one and he gave us the rundown of exactly what happened," Morley said.

At least one parent of each student was present when they were questioned, Morley said.

It’s possible that a judge could decide that the boys should face adult criminal proceedings but that’s unlikely because they don’t have records of prior trouble with the law, Morley said.

Principal Totsy McCraley said the students "most certainly will get a school consequence" along with whatever punishment the judicial system metes out.

Citing privacy concerns, she declined to elaborate.

Morley and McCraley said the investigation was continuing and that they didn’t know whether more students were involved.

"It’s like an onion, you keep turning over layers," she said.

McCraley said she hadn’t run into grade hacking before and was jolted by the discovery.

"I never expect any students to do this kind of activity," she said.