The arrest of 25 students at two Riverside County high schools on Thursday came as a result of two deputies spending a semester undercover on the campuses, officials said.

What they uncovered led to the arrests at Perris High School in Perris and Paloma Valley High School in Menifee, the Riverside County Sheriff's Department said. Investigators seized marijuana, cocaine, methamphetamine, hashish and prescription pills, the department said in a statement.

Perris Union High School District Supt. Jonathan Greenberg told KCAL-TV Channel 9 that the undercover operations were offered to the school district "as an opportunity."

"We didn't hesitate to jump aboard," he said.

After a semester-long investigation, Greenberg said he was notified early Thursday that the arrests would be made at the campuses.

Two of the students arrested are adults -- Serina Ramirez, 18, and Erick De La Cruz, 19. The identities of the other students were not released because they are minors.

The minors were processed at juvenile hall, and the two adults were booked at a county jail.

Greenberg told KCAL that the arrests and scope of the alleged drug operations should not reflect on the school campuses.

“We think those schools, both of them, are great schools, and unfortunately these students were bringing those schools down, in our opinion," he said.

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jason.wells@latimes.com

robert.lopez@latimes.com