The students attended Perris High School and Paloma Valley High School, and two, Serina Ramirez, 18, and Erick De La Cruz, 19, were charged as adults. The arrests on both campuses occurred Thursday, the Los Angeles Time reported Friday.
Investigators seized marijuana, cocaine, crack cocaine, methamphetamines, hashish and prescription pills after an undercover operation at the schools, the Riverside County Sheriff's Department said in a statement.
Police officers are still seeking three more students, KNBC-TV, Los Angeles, said.
"I want the students to know we have ways to deter them from this. It is our obligation to do our best to keep our campuses clean," Perris Union High School District Superintendent Jonathan Greenburg said in an email to parents after the arrests.