The Jordan Middle School teacher's plea change came just days before the scheduled start of his jury trial. Giordano was originally charged with 21 counts of lewd acts on a minor ages 14 or 15.
A judge on Thursday placed a 5-year maximum prison sentence on the plea deal. Giordano is scheduled to appear in court for sentencing on Aug. 22.
Upon his release from prison, Giordano would have to register as a sex offender for the rest of his life.
Giordano, who began teaching at Jordan Middle School in 1991, allegedly engaged in a 3-year relationship with a 14-year-old student in the early 1990s, according to San Mateo County Deputy District Attorney Steve Wagstaffe.
The alleged victim, now in her late 20s and living in Pennsylvania, claims that her sexual encounters with Giordano began in December 1991 after he hired her to baby-sit his son, according to Wagstaffe.
Giordano allegedly molested the victim almost weekly, ending the relationship in March 1994 when she was 17 years old, Wagstaffe said.
The woman did not report the molestations until memories of the encounters surfaced during a counseling session in 2005, Wagstaffe said.
Giordano was arrested at his Menlo Park home on Aug. 18, 2005 and has been free on more than $1 million bail since September.
--Bay City News