The Pew Internet and American Life Project, in a study released Thursday, also found that teens who keep blogs or use social-networking sites like Facebook or News Corp.'s MySpace have a greater tendency to slip nonstandard elements into assignments.
The results may give parents, teachers and others a big :( - a frown to the rest of us - though the study's authors see hope.
"It's a teachable moment," said Amanda Lenhart, senior research specialist at Pew. "If you find that in a child's or student's writing, that's an opportunity to address the differences between formal and informal writing. They learn to make the distinction ... just as they learn not to use slang terms in formal writing."
Half of the teens surveyed say they sometimes fail to use proper capitalization and punctuation in assignments, while 38 percent have carried over the shortcuts typical in instant messaging or e-mail messages, such as "LOL" for "laughing out loud." A quarter of teens have used :) and other emoticons.
Overall, 64 percent have used at least one of the informal elements in school.
Teens who consider electronic communications with friends as "writing" are more likely to carry the informal elements into school assignments than those who distinguish the two.
The study was co-sponsored by the National Commission on Writing at the College Board, the nonprofit group that administers the SAT and other placement tests.
The chairman of the commission's advisory board, Richard Sterling, said the rules could possibly change completely within a generation or two: Perhaps the start of sentences would no longer need capitalization, the way the use of commas has decreased over the past few decades. "Language changes," Sterling said.
Defying conventional wisdom, the study also found that the generation born digital is shunning computer use for most assignments. About two-thirds of teens say they typically do their school writing by hand. And for personal writing outside school, longhand is even more popular - the preferred form for nearly three-quarters of teens.
That could be because the majority of writing is short - school assignments are on average a paragraph to a page in length, Lenhart said.
Among other findings:
- Teens who keep blogs are more likely to engage in personal writing. They also tend to believe that writing will prove crucial to their eventual success in life.
- Parents are more likely than teens to believe that Internet-based writing such as e-mail and instant messaging affects writing overall, though both groups are split on whether the electronic communications help or hurt. Nonetheless, 73 percent of teens and 40 percent of parents believe Internet writing makes no difference either way.
The telephone-based survey of 700 U.S. residents ages 12 to 17 and their parents was conducted Sept. 19 to Nov. 16 and has a margin of sampling error of plus or minus 5 percentage points.