"You don't tell the parents how to raise their kids," she said. "Families ask, 'Who does she think she is?' I have to explain to nannies to tone it down."
But mothers are sometimes out of touch with the realities of everyday child-rearing. Cascio tells new mothers, "Your nanny probably has more knowledge than you do. Respect her opinions and give her credence. You have only book knowledge."
Nannies tell Cascio they spend weekdays teaching children to say "please" and "thank you," but after the weekend, all bad habits return.
"The parents don't want to be bothered, and they give their children every video on the market and anything else they want," said Cascio. "By Monday, it's all undone."
"If the mom and dad say they want the nanny to be creative and educated and read to the child and take nature walks, it's unrealistic to expect them to clean the bathroom, change the beds, dust and do vacuuming," said Cascio.
"They don't want be in a situation where they are busy cleaning the shower and the child opens the door and walks outside or gets caught in the blind cord," Cascio said.
Elizabeth Elder, a New York City mother of two with a baby on the way, has had both good and bad luck with nannies. Her husband works long hours in the financial world and she relies on her nanny not only for child care and housekeeping, but for companionship and advice.
For the last three years, she has had a full-time nanny, Amanda, an older woman from Guyana with a master's in teaching. But soon, she will leave, moving to Canada to seek citizenship.
"Amanda has a gentle, wonderful way about her," said Elder. "She is a terrific foil for me -- calm and distant."
But recently, Elder has tried another nanny, one with an attitude. "She clearly doesn't like children, and they don't like her. She is perfectly responsible; we just don't have the same love for her."
Elder says this new nanny views her role as "just a job," working only the allotted hours and doing the "minimum required." Elder suspects that the minute she leaves the apartment, the nanny flips on the television for the children and talks on the phone.
Ultimately, Elder says she will fire the nanny. But finding another Amanda, who can nurture her children without stealing a parent's emotional thunder, will be difficult.
"You have to be careful, " Elder said. "You trust your nanny with your family's secrets. You don't want her to violate that trust."