Undated (AP) _ For more and more high school students, mousse abuse is taboo. So is hair down to there. And though they don't necessarily have to dress for success, some say they must dress under duress.

Along with perpetual peer pressure to wear ''in'' clothes and sport the latest trendy haircuts - whether it's a Batman insignia or a moussed-up do - American teen-agers are facing dress and hair codes that impose official ideas of fashion.

In a flashback to the '60s, some students are protesting what they consider infringements on their right to free expression.

''It's very regrettable when educators fail to see that kids have rights and that breathing down their necks about ways they should be able to express themselves is not encouraging real education,'' said Leanne Kats, executive director of the National Coalition Against Censorship.

In Henry County, Ga., for example, about 100 students picketed the school superintendent's office last month when dozens of boys were sent home because their hair touched the collar in violation of a new policy.

The same rule in Jasper, Ala., resulted in an angry school board meeting.

Shelia Whitfield, whose son Duane, a 10th-grader, was sent home because his hair is an inch longer than allowed, complained the rule was an invasion of privacy.

''His hair doesn't have anything to do with his education,'' Mrs. Whitfield said.

New dress codes are in effect in several Texas school systems, mostly to guard against offensive or suggestive T-shirts, and in Baltimore, where furs, costly jewelry and leather coats were banned.

Dozens of other systems, including some in Michigan, New York and Louisiana, have adopted voluntary dress codes for their schools to consider.

Gary Marx, a spokesman for the American Association of School Administrators, said stricter dress and hair codes have not yet become a national trend but sentiment is growing to strengthen such rules.

''We do see indications here and there that schools are thinking about dress codes and how students are attired may affect their education and the education of others,'' Marx said. ''I think there is a sense in society that we sometimes act the way we look.''

Lawrence Tribe, a Harvard University law professor who specializes in First Amendment issues, said the U.S. Supreme Court has never dealt directly with the issue and the lower federal courts have ruled both ways.

The high court would likely side with school boards if it ruled today, he said.

''I think it stretches the free expression clause to apply it in schools,'' Tribe said. ''The power of compulsory education already involves a major intrusion into a person's ability to express himself. The school board has a broad range of powers over its students.''

In Baltimore, schools' spokesman Dick Holden said the new code was aimed at eliminating ''the uniform of the drug culture.'' He said the clothes also are too expensive for some students to afford, leading to violence.

''The dress code became a major topic of discussion after some violent incidents in our schools involving outsiders stealing, or attempting to steal, jackets or jewelry of our students,'' Holden said. ''Clothing had become attractions to criminal activity.''

The New Orleans school board instituted a voluntary uniform policy for schools, and spokeswoman Rose Peterson said about 100 schools have ''adopted some kind of uniform.''

She cited three reasons: ''It's a security issue. When the schools are wearing a uniform, it's easy to recognize an outsider. For the parents, they perceive it as a lot cheaper. And it takes the pressure off kids to wear designer clothes.''

In Clovis, N.M., a one-year trial dress code is in effect after students rewrote an old one that banned shorts for boys but allowed miniskirts for girls. In protest, some boys wore miniskirts to school.

The new policy allows shorts and skirts if neither is shorter than 5 inches above the knee.

And in San Antonio, a 13-year-old student was forced to get rid of two Batman emblems emblazoned on each side of his head with bleach. Officials banned him from class until he came back with a flattop.

Among students, though, opinions can be divided.

Many see the restrictions as arbitrary, and others worry that some adults assume a given style of dress means a student is taking drugs or involved in illegal activity.

Still others, including student body President Jason Thompson of Allen High School in Dallas, support policies encouraging neat appearance.

''Fads come and go,'' Thompson said. ''Last year, when stud earrings were allowed for the first time, almost everyone went out and got his ear pierced. But now you don't see earrings that much.''