10 is the new 15 as kids grow up faster

High stakes
But as the limits have been pushed, experts say the stakes are also higher — with parents and tweens having to deal with very grown-up issues such as pregnancy and sexually transmitted diseases. Earlier this year, that point hit home when federal officials recommended a vaccine for HPV — a common STD that can lead to cervical cancer — for girls as young as age 9.

"Physically, they're adults, but cognitively, they're children," says Alderman, the physician in New York. She's found that cultural influences have affected her own children, too.

Earlier this year, her 12-year-old son heard the popular pop song "Promiscuous" and asked her what the word meant.

"I mean, it's OK to have that conversation, but when it's constantly playing, it normalizes it," Alderman says.

She observes that parents sometimes gravitate to one of two ill-advised extremes — they're either horrified by such questions from their kids, or they "revel" in the teen-like behavior. As an example of the latter reaction, she notes how some parents think it's cute when their daughters wear pants or shorts with words such as "hottie" on the back.

"Believe me, I'm a very open-minded person. But it promotes a certain way of thinking about girls and their back sides," Alderman says. "A 12-year-old isn't sexy."

With grown-up influences coming from so many different angles — from peers to the Internet and TV — some parents say the trend is difficult to combat.

Claire Unterseher, a mother in Chicago, says she only allows her children — including an 8-year-old son and 7-year-old daughter — to watch public television.

And yet, already, they're coming home from school asking to download songs she considers more appropriate for teens.

"I think I bought my first Abba single when I was 13 or 14 — and here my 7-year-old wants me to download Kelly Clarkson all the time," Unterseher says. "Why are they so interested in all this adult stuff?"

Targeting younger consumers
Part of it, experts say, is marketing — and tweens are much-sought-after consumers.

Advertisers have found that, increasingly, children and teens are influencing the buying decisions in their households _ from cars to computers and family vacations. According to 360 Youth, an umbrella organization for various youth marketing groups, tweens represent $51 billion worth of annual spending power on their own from gifts and allowance, and also have a great deal of say about the additional $170 billion spent directly on them each year.

Toymakers also have picked up on tweens' interest in older themes and developed toy lines to meet the demand — from dolls known as Bratz to video games with more violence.

Diane Levin, a professor of human development and early childhood at Wheelock College in Boston, is among those who've taken aim at toys deemed too violent or sexual.

"We've crossed a line. We can no longer avoid it — it's just so in our face," says Levin, author of the upcoming book "So Sexy So Soon: The Sexualization of Childhood."

Earlier this year, she and others from a group known as the Campaign for a Commercial-Free Childhood successfully pressured toy maker Hasbro to drop plans for a line of children's toys modeled after the singing group Pussycat Dolls.

Other parents, including Clyde Otis III, are trying their own methods.

An attorney with a background in music publishing, Otis has compiled a line of CDs called "Music Talking" that includes classic oldies he believes are interesting to tweens, but age appropriate. Artists include Aretha Franklin, Rose Royce and Blessid Union of Souls.

"I don't want to be like a prude. But some of the stuff out there, it's just out of control sometimes," says Otis, a father of three from Maplewood, N.J.

"Beyonce singing about bouncing her butt all over the place is a little much — at least for an 8-year-old."

In the end, many parents find it tricky to strike a balance between setting limits and allowing their kids to be more independent.

Plante, in California, discovered that a few weeks ago when he and Zach rode bikes to school, as the two of them have done since the first day of kindergarten.

"You know, dad, you don't have to bike to school with me anymore," Zach said.

Plante was taken aback.

"It was a poignant moment," he says. "There was this notion of being embarrassed of having parents be too close."

Since then, Zach has been riding by himself — a big step in his dad's mind.

"Of course, it is hard to let go, but we all need to do so in various ways over time," Plante says, "as long as we do it thoughtfully and lovingly, I suppose."

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