THE READING and writing will be easy, but it's the 'rithmetic that's bound to get you when you start shopping for school clothes this fall. With clothing prices up as much as 10 percent, and shoe prices as much at 30 percent, many parents are buying fewer, more carefully chosen items and seeking quality that will hold up through heavy use.

"My own clothing costs are up, so I guess I'm not all that surprised that my kids' clothes are, too," says Lynn Oliver of Silver Spring. "But some kids' clothes are beginning to cost almost as much as my own."

Oliver, like many others, is sticking to classic shapes and materials like jeans and corduroys for her 6-year-old son, Taylor. She chooses items that will hold up through many washings, and that her son likes to wear and won't push to the back of the closet.

"Prices are high, so I look for quality in kids' clothes," says Lynda Pattashnick. "Lots of things are passed down, too, and that helps a lot. Clothes that are cheap just aren't worth it in the end."

Stores have picked up on this kind of thinking, and are carrying basic, sturdy items this fall. Just the same, there are enough variations in the classic look to make school wardrobes look new.

Sweaters are in great abundance, along with sweater jackets and sweater dresses. High-schoolers will have the option of skinnier, shorter sweaters that are textured and look handknit even when they are not. Sweaters done in bright color blocks and sweater sets, back to the vintage matching pullover and cardigan are among the options.

Skirts pick up a favorite grown-up theme -- the accordion pleat -- but blat box pleats and kilts are also showing up in traditional tartans as well as oddball plaids.

Designer jeans and jean skirts have added new status names in this high price item. While denim is still part of the assortment, much of the appeal is the variety of color as well as fabrics, including a tiny-wale corduroy that almost looks like velvet, chunky wide corduroy and actual velveteen, in a wide range of bright to classic colors.

The cowboy look starts with jeans and western shirts and finishes off with the cowboy boots that kids are already coveting. The teen set rationalizes spending $60 and up for authentic boots by planning to wear them for all occasions, with skirts as well as pants (tucked in, of course).

The sports look -- including jogging clothes, cheerleader sweaters, status brand sneakers, and football jerseys -- is bound to get a big boost from the upcoming Olympic games. And the roller-skating craze has already spun off its own fashion of flashy socks and satin shorts, shirts and overalls.

If the shapes are classic, the palette offers the option of bright colors in velour tops, jeans and all the accessories.

The clothing that eventually winds up at the cash register will be selected for price tag, appropriateness and need. Laurie Woodard, 14, a student at Hammond High School in Columbia, Md., opts for pants not only because they are generally more comfortable, but also because they are warmer. With her regular two-hour bus ride each way to The Washington School of Ballet, warmth is a consideration -- since the buses are often cold. As for skirts, they are strictly dress-up garb for her. "Besides, it is hard to find skirts with a small enough waist to stay up," says Woodard, size 3.

Julie Funderburk steers clear of kilts because they look too much like her Stone Ridge school uniform. She likes sweaters and pants, and usually opts for the Calvin Klein jeans label. "That's the only way I can get pants that are long enough," says Funderburk, who is 5 feet 10.

The clincher on clothing purchases for school may well be temperature in the classroom. According to Ronald W. Mordecai, deputy director of the District of Columbia Department of General Services, elementary schools will not be required to keep thermostats at 65 degrees, but other schools will be encouraged to do so.

In those schools, the heavy sweather will be the most important garment of all.