It is the latest trend in fall fashion: Workers and students who dress down or show too much skin are being told to button up.

Tired of staff members whom they see as pushing the limits of professionalism and good taste, a growing number of employers are issuing lengthy dress codes, some with photos to illustrate the do's and don'ts. More schools also are getting stricter about student attire.

M.J. Dean, who just began his senior year at the private Cape Cod Academy in Osterville, Mass., discovered new rules at his school when he received the updated student handbook this summer. Among the guidelines: no pants with side pockets, including popular cargo pants, or T-shirts with writing on them -- and "no tight or excessively loose clothing."

"This very strict new dress code is, quite honestly, ridiculous," said the student body vice president, 17. "You can't really represent yourself the way you'd like."

Likewise, some employees think they should be trusted to use good judgment about their clothes. Joe D'Adamo, who works at the Chicago ad agency LKH&S, usually wears jeans, a T-shirt and sneakers to work, and dresses up when he sees clients.

He said a dress code would be "irritating" -- but that has not stopped bosses at some companies.

Effective this month, Target Corp. has a 20-page dress code for employees at its Minneapolis headquarters. Men must now wear a sport coat or tie if they leave their usual work area. Women are required to wear a jacket over any sleeveless blouse; sweater sets are among other options.

The staff at G.S. Schwartz & Co., a New York investor and public relations firm, received a recent e-mail memo asking employees to bump up their apparel choices "at least one more notch."

"For example," the memo read, "we would prefer that properly fitting sweaters be worn with a collared shirt underneath. Certainly, khakis should be neat and clean."

Moreover, "shaving regularly also is a good idea," the memo suggested, "for either sex."

Rachel Honig Peters, a senior vice president at the company, said the e-mail was sent after company officials noticed their clients dressing up more.

Elsewhere, business owners in the service industry say customer complaints are driving them to put tougher dress codes in place.

That was the case for Erika Mangrum, owner of the Iatria Day Spas and Health Center in Raleigh, N.C. She recalled sending one employee home to change after she came to work wearing a cropped T-shirt that showed her stomach and a navel ring.

"This is really tough stuff," said Mangrum, who understands how frustrating dress codes can be for employees. Mangrum herself once got in trouble, more than a decade ago, for not wearing pantyhose when she worked at a major telecommunications firm.

Now, she has had to institute a dress code at her own company -- "no shorts, no denim, no flip-flops." And she is wondering whether she should add rules about piercings.

"How far can and should a company go? We're wrestling with that," Mangrum said. "And frankly, we don't have an answer."

The good news, say those who monitor trends, is that modesty and more formal attire are gaining favor even with teenagers and people in their twenties. Many employers say that young workers are the most frequent dress code offenders.

Tina Wells, the CEO of Buzz Marketing, said anxiousness over the economy, the war in Iraq and the upcoming election have created a mood that is more "focused and serious."

"Besides, how much lower could low-rise jeans get?" quipped Wells, whose New Jersey-based firm compiles feedback from teenage advisers.

In the end, Thomas Evans, headmaster at Cape Cod Academy, said he would rather not have to police student attire. But he said administrators at the K-12 school had little choice after parents of younger students complained about some older students' clothing.

Much the same has happened at schools elsewhere.

In Chicago, for instance, strict dress codes -- and uniforms -- are a matter of safety inasmuch as the way a student wears a pant leg, a bracelet or a hat can indicate a gang affiliation.

And even Dean, the student body vice president at Cape Cod, acknowledged that a few students dressed inappropriately last year.

But he does not think everyone should be punished for the actions of a few. So he and other students plan to meet with their headmaster to see whether he will loosen the dress code.

Asked what he thinks their chances are, Dean sighs and says: "Slim to none."

"This very strict new dress code is, quite honestly, ridiculous," student body vice president M.J. Dean said, sporting clothes no longer allowed on campus. "You can't really represent yourself the way you'd like." Dean and fellow students plan to take their concerns to the headmaster of the Osterville, Mass., school, but he is not optimistic for changes.