A school principal has taken disciplinary action against students after social media posts containing "derogatory" and "vicious" false rumours about staff and pupils appeared online.
Elizabeth Armstrong, head teacher of Enniskillen Royal Grammar School, revealed on Thursday she was taking action after the discovery of "offensive" messages on Instagram.
The PSNI confirmed it was aware of the posts, which have since been removed.
Ms Armstrong spoke out after writing a letter to parents saying the school had been alerted to two Instagram accounts containing "highly inappropriate" and "vicious" false statements.
Her letter, first reported by the Impartial Reporter, also addressed the arrest of a 16-year-old girl who was cautioned by police following the sale of so-called 'cannabis gummies' -sweets which contain illicit substances - at the school.
Enniskillen Royal Grammar, which last year found itself at the centre of an upskirting court case involving a teenage boy who was prosecuted for filming two teachers, suspended four pupils following the discovery of an illegal substance, according to the local newspaper.
The letter, also seen by this newspaper, stresses that while the social media accounts have been taken down, screenshots of the material may still exist and may be in the possession of "several pupils".
According to the head teacher, the first account, which had around 200 followers, was reported to Instagram and the PSNI and subsequently removed.
A copycat account appeared in its place and was also reported and taken down.
Ms Armstrong told this newspaper her school was dealing with both "serious matters" in a "robust and open manner".
"We are treating both situations with the utmost seriousness and the pupils involved have been and will be sanctioned in line with our school behaviour policy," she said.
Ms Armstrong added in a statement that the school was working with the PSNI and other statutory agencies to tackle the problems.
"Our young people face many challenges, pressures and choices in our modern society," the principal said.
"It is crucial that schools work closely with parents in a spirit of open dialogue and communication in acknowledging this and in supporting our young people in making wise choices in an increasingly complex world where drugs and the misuse of social media are all too prevalent.
"It was in this spirit that we wrote to our parents to inform them of two serious issues we have been dealing with in our school community recently. (These) have arisen through pupils making very wrong choices with regard to 'gummies'... and through the posting of offensive memes which are derogatory, inflammatory and highly inappropriate and which include totally untrue statements about pupils and staff.
"We have also addressed both issues openly with our pupils in assemblies and in our personal development curriculum."
The head teacher stressed that it was crucial to have "ongoing dialogue at all levels, in schools, in our homes... about these serious issues, the dangers they pose and the need for our young people to make the right choices".
Justin McCamphill, from the teachers' union NASUWT, said the use of social media to harass or bully its members had been a concern for some time.
"Outside public figures, teachers are perhaps the ones who are most affected by this," Mr McCamphill explained.
"Schools need to adopt a rigorous approach in tackling the problem and where appropriate report the matter to police. Schools also need to deploy the full range of sanctions available."
The PSNI warned young people to think of the consequences of selling drugs or posting abusive material online.
"Anyone that gets involved in this kind of behaviour needs to consider the consequences their actions can have," it said in a statement.
"Therefore, we would always ask individuals to think about what they are doing.
"Don't get caught up in something that could cause concern to others or jeopardise your own future."
The police statement also confirmed the investigation into the cannabis gummies was continuing, with the arrested pupil having been interviewed by officers.