But neither can students be disruptive or lewd or interfere with a school's basic educational mission, the court also has said.
How to strike that balance is the question, particularly since the Columbine massacre and the Sept. 11 attacks have made school officials quicker to tamp down on unruly or unusual behavior.
Other student speech cases making their way through the courts include a student who was pulled from class after taping an anti gay message to his shirt and a middle schooler who got into trouble for a shirt that uses symbols of drugs and alcohol to criticize President Bush.
Unlike the Vietnam protesters who won their court fight in the 1960s, Frederick says he was not staking out a political position with the banner he fashioned with pieces of duct tape as lettering.
"What the banner said was, 'Look here, I have the right to free speech, and I'm asserting it.' I wasn't trying to say anything religious, anything about drugs," Frederick said in a telephone news conference from China, where he now teaches English and studies Mandarin.
An array of groups, from advocates of drug law changes to gay rights backers to supporters of religious freedom, have lined up behind him.
The Bush administration, school boards, antidrug groups, and former drug control directors William Bennett and Barry McCaffrey are supporting the Juneau schools and principal Deborah Morse. They say that the court should support school administrators who impose reasonable limits on student expression and that those limits should extend to promotion of illegal drugs.
"It was the wrong message, at the wrong time and in the wrong place," said former independent counsel Kenneth Starr, who is representing the school district free of charge, in court papers.
Frederick had previous run-ins with school administrators before the banner dispute. He said he first saw the slogan on a snowboard and thought it would make a good test of his rights because, though meaningless, it sounds provocative.
He chose to display the banner during a school-sanctioned event to watch the Olympic torch relay as it passed through Juneau on its way to the 2002 Winter Games in Salt Lake City.
