Nicole Ethel McMillen, 41, of Irvine, was arrested early Sunday morning. She posted $50,000 bail and was released later in the afternoon.
McMillen works as a part-time aide for the Tustin Unified School District, but investigators said she met her alleged victim through a relative.
Authorities said the alleged incidents happened several times over the past six weeks inside her home. McMillen was booked on a felony count of lewd acts with a child after the boy's parents went to police.
Neighbors said McMillen has lived in the upscale gated community called Northpark for several years. They said she lives with her family, including two sons believed to be in their teens and her husband.
"I was extremely surprised," said neighbor Billy Chen. "It's a very quiet neighborhood and Nicole, we see her drive by all the time. And it's a pretty tight-knit community."
Authorities said McMilllen's employment with the school district is not a factor in the case. But residents said they still want better screening at their schools.
"It looks good on paper, but if you don't back it up and check everything out, things like this are going to happen," said Irvine resident Colleen Dunleavy.
"I am totally not shocked, this is going on all over America and we have to stop it," said Irvine resident Mary Quigley.
Detectives said they are concerned there could be more victims. Anyone with information is asked to call Irvine police at (949) 724-7124.