The Supreme Court declined Tuesday to clarify on what grounds public schools may punish students for their off-campus online speech.

The justices have not squarely addressed the student-speech issue as it applies to the digital world—one filled with online social-networking tools such as Facebook, Twitter, MySpace and others. The issue before the justices tests whether public schools may discipline students who, while off campus, use social-networking sites to mock school officials.

The lower courts have been all over the map on the First Amendment issue because they maintain they have been saddled with a Vietnam War-era high court precedent that predates the Internet.

In the leading case of the three petitions the justices declined to review Tuesday, the lower court opinion urged the Supreme Court to end the confusion of whether that older case does indeed still hold in the internet age. The National School Boards Association also urged the high court to review the issue.

The association and others told the justices that “The ubiquitous use of social networking and other forms of online communication has resulted in a stunning increase in harmful student expression that school administrators are forced to address with no clear guiding jurisprudence.”

The 1969 Supreme Court precedent holds that student expression may not be suppressed unless school officials reasonably conclude that it would “materially and substantially disrupt the work and discipline of the school.” In that landmark case, the Supreme Court said students had a First Amendment right to wear black armbands on campus to protest the Vietnam War.

But that precedent, which addressed on-campus speech, is often now being applied to students’ off-campus online speech four decades later—a conclusion that some lower courts have said is out of touch with today’s reality.

The leading case before the justices comes from the 3rd US Circuit Court of Appeals, which ruled last year that local Pennsylvania school district officials overreacted and breached the First Amendment rights (.pdf) of a junior high student who ridiculed her principal online, using a computer off-campus.

But in 2010, the same circuit court with a different set of judges approved of the 10-day suspension (PDF) that the Blue Mountain School District handed the 14-year-old student, who mocked the principal with a fake MySpace profile. The 2007 profile insinuated the principal was a sex addict and pedophile.

In both rulings, the circuit based the decision on the 1969 Supreme Court precedent.

Five judges in the 2011 opinion wrote separately that the courts should abandon that precedent, Tinker v. Des Moines Independent Community School District, because it does not pertain to online speech.