It happened at Harker Middle School, a private school on Blackford Avenue.
The woman, who is an employee of the school, told police she was attacked in a classroom around 6 a.m. A spokesperson for Harker said it was an hour before any students arrived on campus.
The suspect was caught on surveillance camera roaming the campus from 4 a.m. up until the attack happened. He was then seen walking away from the area.
Harker School released a statement that reads:"We are saddened and upset by this incident and are leaning in to provide support and privacy to our employee and to each other. We are cooperating fully with the authorities and providing them any support needed to help in finding the perpetrator. The safety and security of our students, faculty, and staff have always been paramount and we regularly review all protocols for any additional ways we can help keep our community safe. We are hopeful that the efforts of the police and the community will result in a swift arrest."
Police say they will have a presence at the school and increase patrols in the area.
Anyone with information is asked to contact Detective Sergeant Samantha Huynh or Detective Jennifer Majors of the San Jose Police Department's Sexual Assault Investigations Unit at (408) 277-4102 or call "911" with immediate suspect information.
Persons wishing to remain anonymous may either call the Crime Stoppers Tip Line, (408) 947-STOP (7867), or click this link to reachSilicon Valley Crime Stoppers.
Persons providing information leading to the arrest and conviction of the suspects may be eligible for a cash reward from the Silicon Valley Crime Stoppers.