You know how to avoid social media posts that could make adults doubt your judgment and maturity, right? Foolhardy teens in the news probably thought they did too, so learn from their misfortune. The recent graduates were accepted by Harvard University, which now changes its mind because about 10 incoming freshmen shared Facebook memes that were racist, anti-Semitic and mocked sexual assault, domestic terrorism, the Holocaust and child deaths. The self-inflicted damage is so serious and so easily avoided that is raises the question: What were they thinking?

The inflammatory content was posted in a private chat group set up last December, and reportedly was reported to the Ivy League school by members who don't want such insensitive, immature classmates. "The Admissions Committee was disappointed to learn that several students in a private group chat for the Class of 2021 were sending messages that contained offensive messages and graphics," it told offenders. At a larger Facebook group for all incoming freshmen that's moderated, the university warns that Harvard "reserves the right to withdraw an offer of admission under various conditions, including if an admitted student engages in behavior that brings into question his or her honesty, maturity or moral character."

The situation is a reminder that online prudence is vital for students, job-seekers and those in the workplace. Parents and high school counselors routinely tell students that the words, photos and slides they post can hurt themselves and others. Views are mixed among Harvard newcomers who aren’t blocked from enrolling. "People can post whatever they want because they have the right to do that," says Cassandra Luca, who's in the public Facebook group, but not the private chat one. "It wasn't Harvard-affiliated, it was people doing stupid stuff." Another newly accepted student, Jessica Zhang, tells The Harvard Crimson campus newspaper paper the penalty is warranted: "I appreciate humor, but there are so many topics that just should not be joked about. . . Those actions really spoke about the students' true characters. I do not know how those offensive images could be defended."

Commentator says: "The rescinding of their admissions was not only justified, it was necessary. Those spots can and should go to people who will make better use of them. Why reward those poisoned by toxic privilege with more privilege?" – Jeff Yang, a Wall Street Journal columnist writing at CNN.com

Attorney says: "Punishing students academically for their political views or their personal values is a serious mistake. These actions are not consistent with the spirit of the First Amendment. Judging other people's humor, even in the worst taste, just strikes me as somewhat dangerous." – Alan Dershowitz, former Harvard law professor

Author says: "Kids often go online and . . . try on different personalities, different viewpoints, see what kind of response they get -- especially if they're using apps or groups where their real name isn't being used." -- Ana Homayoun, education consultant