Gilbert Olivares was first arrested last week for allegedly touching a student inappropriately. But as the investigation continued, authorities found 14 videos on his computer featuring students.
Police said Olivares was not in the room at the time of the tapings, and the students apparently were not aware there was a secret cellphone focused on them.
One parent, who did not want to be identified, expressed outrage.
"There is always that privilege between your student and the counselor. There was a lot of times that I ask questions, not only of the school, because he was taken out of class, and they said there was privilege there. They couldn't divulge what was going on, so there was a lot of secrecy," said the parent.
Olivares faces at least 19 felony charges, but more are expected as authorities check his four computers.
Olivares, who is being held at the Monterey County Jail, had worked for Sunrise House, an organization that counsels teens on substance abuse. He was not an employee of the Salinas Union High School District, although he worked at the high school for five years.
The Associated Press contributed to this report.