A rise in concerns around primary pupils' use of a social media app has prompted a Sheffield headteacher to write to parents.
Bradway Primary headteacher Paul Stockley said there has been a rise in the number of concerns staff have relating to WhatsApp, particularly with older pupils.
They include the 'inappropriate, offensive and disturbing' language used towards each other during group chats, using WhatsApp at inappropriate times, such as the middle of the night, the amount of messages youngsters are receiving and how pupils are misinterpreting some messages and having disagreements with friends.
He felt it is 'vitally important' that schools work together with parents to raise awareness and increase understanding of the dangers of social media.
He urged parents to find out what apps their children are using and to ensure they are age appropriate.
His assistant headteacher, Annabel Wales, has written to parents outlining the concerns and advice and urging them to be extra vigilant of their children's social media use.
Mr Stockley said: "Social media creates one of the biggest challenges for young people as they grow up, especially when they have free access at a young age.
"When participating in online chat, there is pressure to act in ways that would not be acceptable in face to face interactions and apps like snapchat, WhatsApp and Facebook create pressure to display a 'perfect' public image that is often at odds with the personality and appearance of the real child or young person.
"We find that pupils who are delightful, polite young people in school can sometimes display very different behaviours online in the often mistaken assumption that they are acting anonymously.
"Unguarded and sometimes cruel words cause distress and concern with repercussions in school as children are left feeling upset and distracted.
"Parents are often unaware of what their children get up to online and are genuinely shocked when shown screenshots with evidence of the language used."
He added: "Failure to act can lead to some children creating an extensive, damaging online footprint which can later affect job prospects since some employers will check the content of potential employees' online profile before hiring. It can even lead to police involvement."