Pupils at a private school in Taunton, Somerset, are being taught how to avoid defaming others on social networks including Facebook and Twitter.
"We've been trying to make them accountable – if you wouldn't say something to a person's face, if you wouldn't say it in front of me or your parents, then you don't say it," Carol Manley, a senior teacher at Taunton School, told the Guardian.
"Students need to know that whatever they say may just come back to bite them."
The new lessons come after Lord McAlpine threatened legal action against Twitter users who wrongly linked him to child abuse claims featured in a BBC Newsnight programme.
"We've become increasingly aware as a school that university admissions tutors are now accessing Facebook sites to check up on students," added Manley.