At a certain point, parents loosen the reins -- or, in this case, the belt loops -- to allow space for children to define a personal style of dress.

And, as parents see carefully creased khakis and Dora the Explorer sneakers cast aside for oversized, unbelted blue jeans and open-toed stiletto heels, they know individual style can go only so far before they have to stop it from leaving the house.

But even after careful parental scrutiny, questions remain for school administrators who have to enforce what are often subjective dress code guidelines, and for students who wonder when those guidelines infringe upon their rights to free expression.

Most schools refer to the landmark Supreme Court case Tinker v. Des Moines Independent Community School District, which declared in 1969 that schools do not have the right to censor student expression through their attire unless they can reasonably forecast that a disruption to the learning environment will result from what is worn.

The notion, however, of what will cause a disruption is sometimes not exactly clear until an actual disruption occurs.

Two incidents at Gateway High School this school year exemplify the sometimes questionable nature of dress code enforcement.

In November, several white students were asked to remove T-shirts reading "I [heart] being white."

In February, a Muslim student was asked to remove aT-shirt reading "RIP Israel," and was sent home days later when he refused to take off a kaffiyeh, a scarf that is worn in Arab countries.

Gateway School District spokeswoman Cara Zanella said the school reacted immediately to the disruptions caused in each situation. The students wearing the "I [heart] being white" T-shirts had collaborated to wear them because they took offense to a black student wearing an "I [heart] being black" T-shirt the day after the presidential election.

She said the concerted effort to wear the shirts, along with racially insensitive text messages that went around the school at the time, led the school to ask the students to remove the shirts.

"The principal [William Short] takes every situation and evaluates it on its own merit to determine whether or not the situation calls for us to take some kind of action," Mrs. Zanella said.

"If we know you are orchestrating an event to deliberately cause a problem in the school, we want to stop the problem before it starts."

She also defended the school's initial decision to ask two Muslim students, Mohammad Al-Abbasi and Ahmad Al-Sadi, to remove their kaffiyehs because ethnic tensions between Muslim and Jewish students had begun to boil after the "RIP Israel" shirt was worn.

The district arranged a mediation between students closest to the controversy, and both sides agreed that there were ways to express political beliefs without being offensive or insensitive to others. The school eventually reversed its position and allowed students to wear kaffiyehs.

Woodland Hills High School Principal Dan Stephens said his school hasn't had issues as dramatic as Gateway High School's regarding dress code enforcement, but he acknowledged that the determination of what messages create a "disruption" oftentimes puts administrators in tough positions.

"In most schools, it's a big issue," he said. "Even though it's a dress code issue, it's much deeper than that because [students] use dress as a means of expression.

"What would [administrators] do if someone put on an "I love being gay" shirt?"

Mr. Stephens said his school's dress code was amended at the beginning of this school year to prohibit students from wearing hooded sweatshirts, flip-flops, winter coats and "gang colors" inside the school.

He said all the changes were made "for the safety, health and welfare of students," and that paying attention to "gang colors" would take special effort because the school hasn't actually banned particular colors from campus.

"Gang colors change and gang clothes will change according to what's a symbol to that group of people," Mr. Stephens said. "Just because one or two kids have on red or blue, we don't punish them. But when you see a number of kids wearing red and a number of kids wearing blue and they hang together, it's gang related because they choose to wear those colors together."

Mrs. Zanella agreed that the dress code has to be fluid because of changing styles.

"When dress trends change and hair trends change, we have to take a look at it," she said. "Some kids like wearing big bell sleeves, but for kids working at Forbes [Road Career and Technology Center]. that could be problematic and we have to take a look at it."

Though most revisions to dress codes increase restrictions -- Mr. Stephens cautions that next year saggy pants will be added to the list of prohibited attire -- some administrators have loosened restrictions after viewing the code.

After students at Cornell High School in Coraopolis planned to wear flip-flops to school in a mass protest against a dress code policy in the district, Superintendent Donna Balas said administrators decided to allow older students to wear those shoes to school.

"Kids said female teachers wear flip-flops or open-toed shoes, so that opened up the question of what determines what a flip-flop sandal is," she said.

"I thought, 'Why are we telling them not to wear them?' Sometimes, you have to look at your rationale for why you applied the rule."

But regardless of the rationale, many First Amendment advocates say dress code policies, as a whole, violate student rights.

David Hudson, a scholar at the First Amendment Center, who has written extensively about school dress codes, said schools "have to point to something articulable" that "has already happened" to impose limitations on dress, rather than applying restrictions preventively.

The American Civil Liberties Union of Pennsylvania Web site says school dress codes and uniform policies "often deny students their freedom of expression" and uniform policies "tell you what you must wear to school -- and so they go way beyond just having a reasonable dress code that promotes safety and decorum in schools."

But Mr. Stephens said free expression extends only so far in the professional arena, and it is the school's job to prepare students for the rest of their lives.

"Freedom of speech is a wonderful thing, but as far as school, your workplace, you actually don't quite get to wear what you want," he said.

"You can, but they say, 'Here's the door.' It's a part of growing up."