David Velasquez, 21, faces a possible life sentence on charges of kidnapping and assault with the intent to commit rape, false imprisonment and criminal threats, the San Jose Mercury News reported Thursday.
Velasquez testified that in 2012 he hid behind garbage cans at the Summit Preparatory Charter High School parking garage and then popped out behind the teacher.
He grabbed her, held a knife at her side and ordered her to a car, the Mercury News reported.
The attack ended when another teacher saw Velasquez with the woman and screamed.
He was arrested shortly after the incident at his home.
"This is what they call a senior prank," Velasquez testified. "I decided to do one."
He said his "prank" was supposed to end when he pushed her into the car and slammed the door.
Prosecutors alleged that Velasquez had a sexual interest in the teacher and presented evidence that he had pictures of her on his phone and computer.
Velasquez was being held in lieu of $1 million bail and will be sentenced Nov. 8.