PARENTING : Fads a Mom Could Love : Fall forecasters say kids will be mad for plaid, girls will go for jumpers, and boys will take the droop out of their drawers.

The big news on the Valley fashion front is that grunge--a sloppy look few parents ever went for--is fading into the summer sunset, making pol ished looks more popular.

For fall, girls’ fashions are decidedly more ingenue. Feminine preppy-girl chic is edging out flower-child whimsy. For young men, outrageously oversized styles are being overtaken by a sophisticated, pulled-together look moms and dads are sure to prefer.

“Grunge is over,” agrees Jacqueline Kidd, owner of The Baby Cottage in Woodland Hills. Kidd says the biggest trend for fall is the influx of plaid, for both boys and girls. For boys, she is seeing a tremendous number of woodsy plaid T-shirts a la “Northern Exposure.” The guys will pair these with loose-fitting, pleated corduroys.

At a la popcorn in Woodland Hills, boutique owner Alissa Cohen sees the combination of plaid schoolgirl skirt and fitted, “baby,” T-shirt as a virtual uniform for fall. The shoe of choice to complete the look: French army boots in dark suedes. This trendy footwear is even available in infant sizes at Cohen’s next-door shop, which is called L.A. Babes.

Though brand names are less important in the ‘90s than they were in the ‘80s, Kidd’s store does carry a few some parents and kids like: Baby Guess?, Guess? Kids, Petiza and Wollypogs.

Cohen, who agrees that label consciousness is waning, says many of her sources--such as C.W. Designs--hail from the San Fernando Valley. Value-priced items, not names, are what drive the sales in her boutique, Cohen says.

Parents can expect to pay about $70 for a basic two-piece outfit at The Baby Cottage, while prices at a la popcorn can run from $50 for a preteen outfit to between $40 and $75 for a two-piece outfit for younger girls and boys.

In addition to the plaid fad, jumpers are the most happening trend in girls’ wear, says Kidd. Most of the ones displayed in Valley boutiques like Kidd’s are made of cotton flannel, as opposed to warmer wool styles being shown in the national fashion magazines. Some feature same-fabric suspenders, while others are equipped with detachable leather or vinyl straps. Often the jumpers are paired with crisp white blouses, tiny T-shirts, thigh-high or knee-high socks and sensible shoes.

Cohen says that, at her store, colored denim jeans will continue to be a hot item for both boys and girls. Earthy, subdued tones such as cream and wheat, she adds, are especially popular in early fall when persistent, summerlike temperatures make dark, heat-absorbing colors less practical.

Eight-year-old Shauna Shelton of North Hollywood is readying her list of back-to-school must-haves, says her mother, Laura Leimseider.

Shauna, who selects all her own apparel while shopping with her mother, will be looking for overall jumpers, oversized shorts and long T-shirts.

Leimseider reports that she and her daughter typically shop department stores such as the Broadway, Robinsons-May and Mervyn’s for Shauna’s clothes. Shauna, Leimseider says, places a great deal of importance on style but is still developing her own personal look.

“She’s picky,” says Mom. “She won’t wear anything I pick out. She sometimes doesn’t wear what she picks out.”

One thing Leimseider has determined: If it’s boyish, Shauna usually likes it.

Not all kids bow to the trends when it comes to shopping for back-to-school items. For example, 14-year-old Josh Fradis, who will attend Chatsworth High this year, says temperature is the driving factor for his back-to-school purchases.

Josh--who prefers to shop with his mother because, as he puts it, “she pays when she comes along, otherwise I pay”--plans to get new shorts with his favorite Anchor Blue label.

Though he doesn’t go in for what he calls the really “huge” look, he does have a strategy when it comes to fit.

“I like to buy everything two sizes bigger,” he says, “because it’s all more comfortable that way.” Josh also hopes to round out his wardrobe with some shirts from Billabong, a line of surfing sportswear.

As for the more tailored, preppy look, Josh says that while some of his friends are wearing the classic styles, they aren’t for him.

Parents of children who do favor them, however, says Kidd, are sure to applaud the end of long-heated arguments about too-tight or too-loose clothing.

“There will probably be more agreement among parents and kids,” she predicts. “The trendy clothes will be the ones parents want to see their children wearing, and that’s a welcome change.”