PHILADELPHIA - Two U.S. teens cannot be disciplined at school for MySpace parodies of their principals created from off-campus computers, a federal appeals court ruled Monday.

The postings, however lewd or offensive, were not likely to cause significant disruptions at school and are therefore protected under previous Supreme Court case law on student speech, the 3rd U.S. Circuit Court of Appeals found.

"Today's court decision states that you cannot punish students for off-campus speech simply because it offends or criticizes (school officials)," said Witold Walczak, legal director of the American Civil Liberties Union of Pennsylvania, which represented both students.

However, six judges who dissented in one case said they feared salacious online attacks against school officials would go unpunished.

"It allows a student to target a school official and his family with malicious and unfounded accusations about their character in vulgar, obscene, and personal language," Judge Michael Fisher wrote in the ruling involving the one school district in Pennsylvania.

In that case, an eighth-grade girl created a MySpace page using an actual photo of the principal with a fake name, and purported that it was posted by a 40-year-old Alabama school principal who described himself -- through a string of sexual vulgarities -- as a pedophile and sex addict. The Internet address included the phrase "kids rock my bed."

"Though disturbing, the record indicates that the profile was so outrageous that no one took its content seriously," the 3rd U.S. Circuit majority wrote Monday, overturning its own prior ruling. "(The girl) testified that she intended the profile to be a joke between herself and her friends."

In the other case, student Justin Layshock created a parody that said his principal smoked marijuana and kept beer behind his desk. The district said it substantially disrupted school operations and suspended him, but the suspension was overturned by a district judge, the appeals panel and now the full 3rd Circuit.

In a rare move, the full court had heard oral arguments last year after separate three-judge panels issued conflicting rulings in the twin cases.

Such disparities are common around the country as school districts wrestle with how to address online behaviour that can range from pranks to threats to cyberbullying. The New York-based 2nd U.S. Circuit has upheld school discipline in two similar cases but neither has reached the Supreme Court.