ATLANTA (CNN) -- Only 7 percent of American teenagers learn about sex from their parents, according to a recent Time/CNN poll. However, there is a new mission to bring the "big talk" back home.

Usually by the time parents get around to explaining sex, their children already know the facts of life -- more or less.

But a surprising new theory urges parents to start talking about sex early, gradually giving children details and having the "big talk" by age 8.

Described in the book, "How to Talk To Your Child About Sex," author Richard Eyre's approach is endorsed by leading child psychiatrists.

"Eight is like a window," he said. "The child is not cynical yet, and they do not have the raging hormones yet. Yet they are very conceptual."

Eyre practices what he preaches. He's made the eighth birthday talk a ritual with each of his nine children. It's a conversation that lasts through the teen-age years.

His daughter Charity, 12, said learning about sex at home, at an early age, has strengthened the bond with her parents and helped her to formulate her own convictions.

"My reaction was just like, I was in a stage in my life where I just thought that it was so cool that I knew more about something than my friends did," she said. "I was just so excited that I knew that it was so special that I was going to save it."

In a world where children are bombarded with messages of sex, from the scandal at the White House to MTV, many parents wonder how much influence they can have. Is teaching abstinence, for example, realistic in this day and age?

Eyre said too many parents give up on the idea too easily.

"Here are the facts -- they are very simple and easy to remember: 50 percent of high school kids have never had sex. Of the 50 percent who have, half of them, 50 percent, again say they wished that they hadn't," he said.