Tucson police say five Flowing Wells High School students were arrested Wednesday night on suspicion of conspiracy to commit first-degree murder. A knife was found in one student's possession.
Police went to the school Wednesday after another student told a school employee of the alleged plot.
Investigators are not saying the motive for the plan but say the students were having a problem with another student in their group.
Police arrested 18-year-old Christopher Gibson, 17-year-old Anastasia Lakin, 17-year-old Jessica Good, 15-year-old Gabriel Quiroga, and 15-year-old Andrew Totten.
Tucson Police say all students are being charged as adults.
KGUN-TV reports police Sgt. Pete Dugan said it's fortunate that the student "stepped up and did the right thing."
Flowing Wells School District Superintendent David Baker the alleged plot surfaced because the student trusted an adult and that adult contacted police.
All were booked into a Pima County Jail on charges of conspiracy to commit first-degree murder.
Copyright 2015 The Associated Press contributed to this story.