Keystroke logging, or keylogging, software covertly tracks which keys are struck on a computer keyboard and it is most often used to steal passwords.
Published reports say the four Dickinson High School students, ages 15 to 17, allegedly used the software to gain teachers' log-on information, then changed their own grades and potentially the grades of their friends.
Board of Education President Sudhan Thomas says the grades of as many as 10 students were changed. The students were arrested Friday at the Jersey City high school.
Dickinson is Jersey City's largest high school, with about 1,800 students.