One male officer began posing as a student when classes started in August at Chapparal High School, and a female officer was undercover at Temecula Valley High School, the school district confirmed.
Student Ruben Arreguan said the male officer, whose name was not reported, was in his tech core class, along with three of the students who were arrested.
"To me, he was just a regular high school kid," Arreguan said of the cop.
Four girls and 18 boys were arrested, two of whom were adults. Fifteen students were from Temecula Valley High School, five from Chapparal High School and two from a continuation school for students at risk of not graduating. They possessed and/or sold heroin, LSD, ecstasy, methamphetamines and coke, KCBS-TV, Los Angeles, reported Wednesday.