Pupils shared "inappropriate" photographs on Snapchat and were groomed by paedophiles during lessons on school iPads, it has emerged, after the school head wrote to parents.

One underage girl watched footage of a man performing a sex act via Skype during a lesson on the tablet computer given to all students.

An inappropriate picture was also found on two pupils' Snapchat accounts at Honywood Community Science School in Coggeshall, Essex.

Simon Mason, the school's head, wrote to parents expressing his concern and said that the iPads, which were handed out to all 1,200 pupils, would be upgraded in a bid to prevent further security beaches.

He said one "learner" ignored guidance about befriending strangers online and had been "coerced into sending inappropriate images to someone whose only rationale for 'meeting' the learner on line was to exploit them".