Police said they began their investigation on Nov. 18 after they were informed of a possible incident of child sexual abuse.
They said they learned that the victim, who is now 14, has allegedly been in a sexual relationship with the suspect, 29-year-old Mia Cummings of Oakland, since he was 12.
The investigation revealed that Cummings was employed at the All Saints Catholic School as an after-school program assistant while the boy was a student at the school, police said.
Cummings was arrested on Nov. 26 and was booked at the Hayward police jail on multiple felony counts of lewd acts with a child, police said.
Cummings, who already has been arraigned, currently is in custody at the Santa Rita Jail in Dublin where she is being held in lieu of $800,000 bail.
She has been charged with eight felony counts, including oral copulation, forced oral copulation and contacting a minor with the intent to commit a sex crime. She is scheduled to return to Alameda County Superior Court in Hayward on Jan. 7 to enter a plea.
Hayward police Officer Mark Quinn said in a probable cause statement that Cummings supervised the boy while he attended the after-school program, and developed a relationship with him in which she would stay in communication with him by cellphone calls and text messages.
The boy told police of at least 10 separate incidents in which Cummings would orally copulate him, Quinn said.
Five of the incidents occurred in the school's kitchen when the boy was only 12, and five other incidents occurred off campus, including one in Cummings' apartment, according to Quinn.
Prosecutors alleged that the incidents occurred between Dec. 1, 2011, and earlier this month.
Hayward police said administrators at the All Saints Catholic School have cooperated with the investigation and that they have no indication that Cummings victimized any other children.
All Saints Catholic School officials weren't immediately available for comment today.
