Schools have been told they must be on the alert for pupils who are at risk of "radicalisation" by extremist politics.
New guidance sent to all head teachers by Education Secretary Michael Gove says that "staff members working with children should always think 'it could happen here' where safeguarding [of pupils] is concerned".
Guidance accompanying his letter lists the telltale signs that a pupil could have fallen prey to Islamic or fascist extremists.
These include day-to-day behaviour of the pupil becoming increasingly concentrated around an extremist ideology, changing their style of dress, particularly in a sixth form or further education college where school uniform has been relaxed, and loss of contact with other friends not associated with extremist ideology.
in addition, they could be using "insulting" or "derogatory" terms to describe other groups opposed by the extremists.
Channel, a counter-terrorism project set up by the Home Office, says the most common threat to pupils is from al-Qa'ida supporters or groups adopting the swastika as their emblem.
A recent report from the Channel project described how a seven-year-old had been one of 228 people had been identified as having fallen prey to extremism. 90 per cent of them were aged between 15 and 24.
The new guidance also calls for schools to be on the lookout for other issues, such as pupils coming under pressure from or joining gangs, female genital mutilation and pupils under pressure to succumb to forced marriages.
The guidance says: "Schools and college staff are particularly important as they are in a position to identify concerns early and provide help for children to prevent concerns from escalating."