Fifty Berkeley High School students are accused of hacking into the school's attendance system.
School leaders said some of the students were being paid by classmates for clearing their unexcused absences from school records. The attendance changes affected records between October and January and meant that students could skip classes without their parents knowing.
Administrators first noticed the discrepancies in December. They spent months chasing paper and cyber-trails before confronting students just before spring break.
The loopholes in the system have since been closed.
The Associated Press contributed to this report.