COMMACK, N.Y. (CBSNewYork) – Three Commack High School students allegedly hacked their school’s computer system and altered grades and schedules, police said.

The hack impacted the schedules of some 300 students of the Commack Union Free School District, Suffolk County police said.

Two students had their grades changed, investigators said.

Daniel Soares, Alex Mosquera and Erick Vaysman, all 17 years old, were arrested.

Soares faces charges of burglary, computer tampering, identity theft, computer trespass and eavesdropping charges.

“[Soares] entered into the school after hours, into classrooms, and installed hardware commonly referred to as a key logger, or keystroke logger, he installed it onto a computer that the teachers would use and he would go back a day or two later and retrieve the device after hours when the school was closed,” Detective Sgt. John Best told 1010 WINS. “Any teacher that logged onto that computer and accessed the school network from that computer, he had their password and username. And then, with that password and username, he was able to access the computer network at any time from any computer outside the network and access the teacher’s accounts.

“In one case, I believe he changed a grade that was a 94 to a perfect score of a 100,” Best told WCBS 880’s Sophia Hall.

Vaysman and Mosquera face computer tampering and criminal solicitation charges.                                                                                            

It was district leaders who noticed changes were being made without authorization, CBS2’s Emily Smith reported. Best said detectives were called in, and found evidence of  Soares at the scene — which lead to a search warrant at his home, and ultimately the arrest.

Because the scheduling changes happened in July, the students were not adversely affected, Best said.

The school said all the altered schedules and grades were fixed, and that a full electronic security review is underway, 1010 WINS’ Mona Rivera reported.

“I didn’t even know that there were students in our school capable of this,” Andrew, a junior at Commack High School, said. “But I’d be glad if they put that to good use, instead of the use they’ve been putting it to, which is hacking and creating problems for so many students.”

The investigation continues.

Anyone with any information is asked to call authorities at 631-852-6279 or Suffolk County Crime Stoppers at 800-220-TIPS.