Teachers are expected to bear long days, challenging students and demanding parents. Now, apparently, some teachers are baring too much of themselves.

School boards and superintendents are increasingly pursuing dress codes for teachers. At issue is the same kind of questionable attire most often associated with students.

In some districts, teachers can get dressed down for wearing skimpy tops, short skirts, flip-flops, jeans, T-shirts, spandex or baseball caps. Spaghetti is fine in the cafeteria, but tops held up by spaghetti straps are not welcome in the classroom.

District 11 in Colorado Springs, for example, prohibits sexually provocative items such as clothing that exposes "cleavage, private parts, the midriff or undergarments," district rules say.

In Georgia's Miller County, skirts must reach the knee. Elsewhere in the state, hair curlers are not allowed in Harris County and male teachers in Talbot County must wear ties two or three times a week.

"There's an impression that teachers are dressing more and more -- well, the good term for it would be 'relaxed,' " said Bill Scharffe, director of bylaw and policy services for the Michigan Association of School Boards. "Another term for it would be 'sloppy.' "

Regulating dress is touchy, teachers say.

Teachers may view policies that get too specific as restrictive and demeaning. And what to do about broad policies that are enforced inconsistently? What works for a physics teacher may not fit a kindergarten teacher who sits with students on the floor.

"Because we work with children, and we're trying to relate to them, sometimes we need to have guidelines that say, 'You know folks, here's the line, and you really need to stay on this side of it,' " said Karen Moxley of Grapevine, Tex., who teaches gifted seventh-graders.

But, she added, "I don't know that it needs to go down to what style of outfit you wear."

Moxley spoke during a group interview during the annual meeting of the National Education Association earlier this month.

School administrators say inappropriate dress is most often an issue with younger teachers, whose trendy clothing and casual style can make it hard to distinguish them from their students.

Mark Berntson, who teaches high school band in West Fargo, N.D., wears a tie each day. It is a tradition he began years ago to stand out from his students. He does not wear blue jeans to class often, saving them for occasions such as the first day of the baseball season.

"I don't think I'm taken as seriously if I'm dressed down and I don't think I take my job as seriously if I'm dressed down," he said. "When I dress more professionally, I think I teach better, I think I'm received better, and I think I show more respect for my profession."

Schools usually have exceptions, such as allowing gym teachers to wear shorts. But sometimes the trouble is in finding the line -- literally.

At the Tangipahoa Parish School System in southeastern Louisiana, the dress code was recently updated to let women wear cropped pants that stretch almost to the ankle. But the school board still does not allow Capri pants because those stop only around the mid-calf.

In Houston, the Aldine Independent School District's policy is cut-and-dried: Male teachers must keep their hair above the collar. Their sideburns cannot extend beyond the earlobe. Mustaches may not be of the "Fu Manchu" variety.

This year in Alabama, Birmingham school superintendent Wayman Shiver Jr. tried to ban such attire as excessively tight clothing, see-through tops, and blouses with revealing necklines.

But city school board members have directed him to scale back his plan in favor of a more generic policy. They do not want their administrators to become the fashion police.

"What's too short? What's too long? What's too provocative? What's too revealing?" said Jacqueline Oglesby, a representative for the Alabama Education Association, which worries about unfair enforcement of a dress code. "Everyone has their own definition. And besides, this is supposed to be about the education of children, not tattoos or holes in your tongue."

On the Hawaiian island of Oahu, where Aaron Paragoso teaches music, neat and casual clothes are the norm. He wears a tie when sixth-graders graduate from his school, telling them: "I'm congratulating you by dressing up in this manner. It shows that I'm very proud of you."

Teachers set the example, said Scharffe, the Michigan official and former director of school personnel. That is why he once sent home a teacher whose belt buckle featured a marijuana leaf.

Schools must balance their right to enforce reasonable rules against the freedom of expression that employees have under the First Amendment, said Lisa Soronen, staff lawyer for the National School Boards Association. School lawyers often determine a dress code "might be a nice idea, but it might not be worth the time and headaches to go through with it and do it."