What parent with a VCR doesn't know the real function of the fast-forward button on the remote control?

"Just believe me, Mom. We hear a lot worse at school every day. . . . We're used to it . . . All my friends have seen it . . . You can fast-forward through the bad parts . . . "So the kids shut their eyes, peeking through the slits. Mom or Dad diligently presses with a thumb. Swear words, blood and gore and/or sex blur by. Innocence is saved from ruin for another Saturday night!

As one mother observes: "Fast forwarding through the sexy parts has become responsible parenting."

Needless to say, the VCR's addition to family life has been a mixed blessing.

Just as it's allowed parents to share wonderful educational and entertaining movies with their kids, it's also forced them to play Solomon and Censor more often than they ever expected. All while trying not to turn their kid into a social nerd.

One day, they were thrilled to rent "The Sound of Music" for their children. Then in no time, it seemed, they were debating the side effects of "Nightmare on Elm Street."

What once was a family treat, a planned experience, also became common fare. Indeed, the Christmas season, with kids out of school, is the boom time for video-rental stores. But those soaring holiday rentals aren't reflected in children's titles.

Today's young video sophisticates "fly right to the Nintendo or new releases," says Keith Leopard, a product manager with Trient Partners, which owns the local franchise for Blockbuster Videos.

If the kid has a choice between "Winnie the Pooh" and "Back to the Future III," guess which one he chooses?

"I think we have to face the world we live in. And we live in a video world . . . What we can do is make it work for us," says Diana Huss Green, editor of Parents' Choice Magazine in Massachusetts.

Huss is also editor of "Parents' Choice Guide to Videocassettes for Children," a book published by Consumer Reports. It aims to bring children videos "that will help expand their lives, their vision and their sense that everything is possible."

The guide's critics, from across the country, recommend 300 of the best titles for children on the market. "The Terminator" is not included.

Most parents want to choose what's edifying, but often end up renting what's popular. "Edifying" is frosting on the cake.

"I try to limit the violence he watches," says Bob Simpson of his fourth-grade son. "Horror movies aren't even open for discussion,"

But "it's not always something I have a say in."

His son saw Arnold Schwarzenegger's "Total Recall" at a friend's house before Simpson did. The movie has been described as a thrill-a-minute futuristic tale, rated R for strong violence and profanity.

"You gotta understand how they (the kids) scam on the parents," says Simpson."I can't stop him from seeing it somewhere else."

Simpson says he'd much prefer a diet of Disney for his children and he has no problem with their seeing good science fiction. But, he adds, kids today are so inundated with media messages it's nearly impossible to so limit their viewing.

All a parent can do is try to instill proper values and hope they sink in, he says.

Adds Mike Poor, owner of a video store:

"I think most people do care. But how much are you going to gag them? How much are you going to lock them in the closet?"

Poor will not rent R-rated movies to children unless their parents OK it on their membership card, and provides free religious films to families.

So, how should parents decide what's appropriate viewing?

"On an individual basis you just have to explore your own child and your own relationship with your child," says Pamela Sowell, a school counselor and parent to a sixth- and a ninth-grader.

There are so many potential battlegrounds with kids these days, it's important for parents to choose what areas they feel strongly about, she says, or they could be fighting with their kids about everything - all the time.

Standards, of course, differ from family to family. In some, almost anything goes. In others, it's G or PG for as long as possible. By mid- to late grade school, many parents seem to decide PG-13 is OK.

Since there's no time to preview every film, they rely on word-of-mouth and wish the ratings were more specific.

All this is not to say only current videos are troubling. Sometimes old classics espouse values - such as sexism or prejudice - that parents find offensive.

Not surprisingly, the parents of preteens and teens caution: "the older they get, the less control you have."

Sleep-overs at somebody else's house may present the trickiest situations.

"You don't really know what's going to happen," says Gail Irving, mother of a soon-to-be 13-year-old girl and 3-year-old boy.

Recently, her daughter attended a sleep-over where R-rated "Pretty Woman" - about a prostitute winning the love of a handsome, hot-shot business tycoon - was shown.

One of the girls attending the party brought the movie and caught the hosting mother off-guard.

So the mother phoned every parent to ask permission for their child to view it.

The hosting mother promised to watch with the girls and fast forward through the "sexy parts." If Irving objected, her daughter could go to a separate room while the movie was showing.

Rather than single her child out from the rest of the group, she allowed her to watch the movie.