Just after midnight on Sunday, Barbara Wilson, a 50-year-old school teacher living in Dayton, Ohio, made a post on her Facebook wall that is becoming a familiar refrain for educators on social networking sites.

“I need to let all my students that I am friends with on facebook know that I have to delete them as friends. Our school district does not want teachers and students to be friends for liability purposes,” Wilson wrote. “I will message each of my students personally so you won't be offended. Just know that I really do care about you!”

A new school years means a new round of questions about student-teacher interaction on social networks like Facebook. This year’s debate is being fueled by a ruling last week by a Missouri circuit court judge to grant a teachers’ union a 180-day, preliminary injunction that blocks implementation of a law that would have put strict curbs on how teachers interact with students using social media.

The Missouri State Techers Association had filed the complaint, saying the proposed law infringes on teachers’ free speech rights. The ruling for the injunction found that there are several work-related uses for teachers using social media, and that the law may go too far in curbing what teachers do online in their personal lives.

“This gives everyone time to debate and discuss the issue to come to a proper resolution rather than rushing to piece together language that doesn’t resolve the concerns of educators or allow time for teacher input,” Gail McCray, MSTA Legal Counsel, said in a statement.

Reaction to last week’s ruling in the very online communities the law targeted was mixed.

“But did the students ask for this?” Eric Plaskonos of New York wondered in a Tweet.

Some saw the law, which also bans teachers from communicating with students via text message, as a knee-jerk reaction. The law was called the Amy Hestir Student Protection Act, a Missouri public schools student who was repeatedly molested by a teacher several decades before the creation of Facebook and before the Internet became a main part of elementary and secondary education.

“So it's illegal for teachers to add students or former students as friends on facebook, ‘in order to curb sexual relationships.’ And since the law is zero tolerance a woman and teacher from Missouri got a nice visit from the police because she was talking to her OWN CHILDREN on facebook,” Cale Black wrote on his Facebook wall. “You're kidding me right?!?!!!”

Even if their rights are Constitutionally-protected, as the Missouri ruling implies, some teachers aren’t taking chances. Many teachers choose to not be on Facebook at all, while others set up separate accounts to communicate with students and their friends.

And even that, apparently, was not enough for one teacher at the Arroyo Middle School in California’s Tustin Unified School District.

“Due to the controversy of teachers and students being friends on Facebook, I am disabling this account. When you turn 21 find me on my regular account! ♥,” Caren Oliver posted on Sunday on the Facebook page she had set up for students.