Forget baggy jeans and midriff-baring T-shirts this year’s back-to-school fashion craze consists of navy blue trousers and jumpers, plain white sport shirts and sensible shoes.

It’s not the kids who have gone conservative as much as their parents, teachers and school administrators, who are jumping on the dress code trend with a vengeance making the school uniform, long the plaid province of Catholic schoolchildren, a new and profitable niche for apparel designers and retailers.

“The growth has been spectacular,” said Sylvano Mizrahi, West Coast sales manager for New York-based Lollytogs Ltd., one of the nation’s largest school uniform manufacturers, which sells the garments in Target, Wal-Mart and other discount department stores.

From his office at downtown’s CaliforniaMart, Mizrahi has seen his sales jump 50 percent from 1996 to 1997. Sales are projected to grow another 30 percent this year.

It’s not hard to see why. The market for school uniforms just keeps getting bigger especially in Southern California, which has led the uniform trend since Long Beach became the first of the nation’s 16,000 school districts to adopt a dress code in its elementary schools in 1994.

Since then, more than 30 states have passed laws allowing school districts to require students to wear uniforms.

Locally, districts from Inglewood to Lynwood to Monrovia have adopted dress codes. More than 400 of the L.A. Unified School District’s 660 K-12 schools have implemented uniform policies up from about 300 in 1995, according to LAUSD administrator Jeri Durham.

All that activity is remaking the school uniform marketplace, which until recently was dominated by specialty manufacturers and retailers who focused primarily on private schools.

A good example of those changes is the recent licensing deal between Simi Valley-based Bugle Boy Industries Inc. and Lollytogs to create uniforms bearing the popular Bugle Boy brand name.

Under the agreement, the uniforms are designed, manufactured and shipped by Lollytogs and marketed under the Bugle Boy name. The uniforms are sold in mid-market retail chains, including Mervyn’s, Sears and Kids R Us.

“We see it as a large, growing market,” said Howard Finelt, vice president of licensing for Bugle Boy. “As school boards begin moving toward (mandating uniforms), we want to be part of it.”

Of course, selling uniforms is quite a bit different from marketing sportswear.

For one thing, uniforms are considerably less expensive than regular sportswear, which means narrower margins and tougher price competition. Most manufacturers boast that they can outfit a child for between $100 and $200 a year, far less than the approximately $300 parents spend per child on back-to-school wear annually.

What’s more, there is little product differentiation. Instead, companies are forced to compete largely on the basis of quality, rather than image or fashion.

“Parents have a much higher expectation on the performance of a uniform than they do on regular sportswear,” said Mike Singer, chairman and CEO of Pacoima-based Strategic Partners Inc., which markets uniforms under the Cherokee and Classroom brands.

But that may be changing. Besides Bugle Boy, other mainstream brand names, such as Gap Inc. and Levi Strauss, have jumped into the marketplace.

In fact, L.A. designer Clotee McAfee is basing her entire strategy on creating a brand-name uniform for high school students. Last month, she opened a boutique at Macy’s in the Baldwin Hills Crenshaw Mall to test her label, Uniformity, which features 13 different looks for students, including bomber jackets, vests and wraparound skirts all designed in gray, black, khaki and white to conform with school color requirements.

“We want to give them fashion,” McAfee said. “In order to get high school kids into uniforms, we have to do it the way they buy. And that means creating a label.”