Attebury, who was the band teacher at El Modena High School in Orange, has denied having sex with the teen.
"I had ideas, but I didn't do anything about them," the teen testified, according to City News Service.
According to a deputy district attorney, the relationship became sexual and in early 2008 Attebury moved near the boy to a house where they had sex frequently.
Attebury has been charged with seven felonies including two counts of unlawful sexual intercourse with a minor younger than 16, and dissuading a witness from a crime.
Toward the end of their relationship, parents said they spotted Attebury with the student in the bleachers at a school event with her legs wrapped around him. The parents told the principal and the principal then alerted police.
The story takes another turn. Former student Miguel Lopez, now 23, tried to blackmail Attebury after somehow finding out about the affair. Lopez demanded nude photos and thousands of dollars from Attebury in exchange for his silence.
Attebury never paid Lopez money, but did give him nude photos of herself. Lopez has since admitted to his blackmailing attempts and has been given three years of probation.
Attebury claims she is innocent, although the district attorney's office said they have thousands of sexually explicit text messages that she allegedly sent to the 15-year-old while the two were in a relationship.
If convicted, Attebury faces up to seven years in state prison.
The Associated Press contributed to this report.