The letter has only recently been reported by local media.
The New Paper understands a police report has been made.
The principal's letter did state, however, that students could be subject to possible disciplinary action if their behavior was found to be "inappropriate for the school environment.
Offenders can be jailed for up to five years, fined or caned.
Noting the proposed changes are a step in the right direction, she added: "Persons can no longer use social media to get revenge without being dealt with by the law, given that something posted online is difficult to remove and can leave indelible scars on victims," she said.
Officer MacKenzie cautioned parents to get involved in their children's social media accounts to monitor what they are doing.