Faced with scandals and complaints involving teachers who misuse social media, school districts across the country are imposing strict new guidelines that ban private conversations between teachers and their students on cellphones and online platforms like Facebook and Twitter.

The policies come as educators deal with a wide range of new problems. Some teachers have set poor examples by posting lurid comments or photographs involving sex or alcohol on social media sites. Some have had inappropriate contact with students that blur the teacher-student boundary. In extreme cases, teachers and coaches have been jailed on sexual abuse and assault charges after having relationships with students that, law enforcement officials say, began with electronic communication.

But the stricter guidelines are meeting resistance from some teachers because of the increasing importance of technology as a teaching tool and social media to engage with students. In Missouri, the state teachers union, citing free speech, convinced a judge that a new law imposing a statewide ban on electronic communication between teachers and students was unconstitutional. Lawmakers revamped the bill this fall, dropping the ban but directing school boards to develop their own social media policies by March 1.

School administrators acknowledge that the vast majority of teachers use social media appropriately. But they also say they are increasingly finding compelling reasons to limit teacher-student contact. School boards in California, Florida, Georgia, Illinois,B Maryland, Michigan, Missouri, New Jersey, Ohio, Pennsylvania, Texas and Virginia have updated or are revising their social media policies this fall.

"My concern is that it makes it very easy for teachers to form intimate and boundary-crossing relationships with students," said Charol Shakeshaft, chairwoman of the Department of Educational Leadership at Virginia Commonwealth University, who has studied sexual misconduct by teachers for 15 years. "I am all for using this technology. Some school districts have tried to ban it entirely. I am against that. But I think there’s a middle ground that would allow teachers to take advantage of the electronic technology and keep kids safe."

Lewis Holloway, the superintendent of schools in Statesboro, Ga., imposed a new policy this fall prohibiting private electronic communications after learning that Facebook and text messages had helped fuel a relationship between an eighth grade English teacher and her 14-year-old male pupil. The teacher was arrested this summer on charges of aggravated child molestation and statutory rape, and remains in jail awaiting trial.

"It can start out innocent and get more and more in depth quickly," said Holloway, a school administrator for 38 years. "Our students are vulnerable through new means, and we’ve got to find new ways to protect them."

Holloway said he learned of other sexual misconduct cases when consulting with school administrators around the nation about social media policies. While there is no national public database of sexual misconduct by teachers, dozens of cases have made local headlines around the country this year.

In Illinois, a 56-year-old former language-arts teacher was found guilty in September on sexual abuse and assault charges involving a 17-year-old female student with whom he had exchanged more than 700 text messages. In Sacramento, a 37-year-old high school band director pleaded guilty to sexual misconduct stemming from his relationship with a 16-year-old female student; her Facebook page had more than 1,200 private messages from him, some about massages. In Pennsylvania, a 39-year-old male high school athletic director pleaded guilty in November to charges of attempted corruption of a minor; he was arrested after offering a former male student gifts in exchange for sex.

School administrators are also concerned about teachers’ revealing too much information about their private lives. As part of a policy adopted last month in Muskegon, Mich., public school employees were warned they could face disciplinary charges for posting on social media sites photos of themselves using alcohol or drugs.

"We wanted to have a policy that encourages interaction between our students and parents and teachers," said Jon Felske, superintendent for Muskegon’s public schools. "That is how children learn today and interact. But we want to do it with the caveat: Keep work work — and keep private your personal life."

New York City, the nation’s largest school district, has been at work on a social media policy for months and expects to have one in place by spring. In the meantime, controversies over social media erupt regularly, like one earlier this month over a Bronx principal whose Facebook page included a risque picture that was then posted in the hallways of her school.

Richard J. Condon, special commissioner of investigation for New York City schools, said there had been a steady increase in the number of complaints of inappropriate communications involving Facebook alone in recent years — 85 complaints from October 2010 through September 2011, compared with only eight from September 2008 through October 2009.

What worries some educators is that overly restrictive policies will remove an effective way of engaging students who regularly use social media platforms to communicate.

Nicholas Provenzano, 32, who has been teaching English for 10 years at Grosse Point High School in Michigan, acknowledged that "all of us using social media in a positive way with kids have to take 15 steps back whenever there is an incident." But he said the benefits were many and that he communicated regularly with his students in an open forum, mostly through Twitter, responding to their questions about assignments. He has even shared a photo of his 6-month-old son. On occasion, he said, he will exchange private messages about an assignment or school-related task. He said that in addition to modeling best practices on social media use, he has been able to engage some students on Twitter who would not raise their hand in class.

He also said social media networks allowed him to collaborate on projects in other parts of the country. Facebook offers guidance for teachers and recommends they communicate on a public page. Some teachers, however, favor a sharply defined barrier. In Dayton, Ohio, where the school board imposed a social media policy this fall, limiting teachers to public exchanges on school-run networks, the leader of the teachers union welcomed the rules. "I see it as protecting teachers," said David A. Romick, president of the Dayton Education Association. "For a relationship to start with friending or texting seems to be heading down the wrong path professionally."

© 2011 The New York Times Company