A total of 4,611 people, half of them children and teens, have been flagged for possible intervention by UK government's Channel programme to prevent them from falling prey to extremist ideology.
Figures released by UK's National Police Chiefs Council under the Freedom of Information Act showed that between July last year and the end of June this year there were 2,311 referrals relating to under-18s - an increase of 83 per cent compared to previous year.
As an enhanced Prevent duty took effect last year, school referrals rose to 1,121, more than double the 537 in the previous year.
The prevent duty falls under UK's Counter-Terrorism and Security Act and imposes a requirement for "specific authorities to have due regard to the need to prevent individuals from being drawn into terrorism".
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It means that councils, schools, health services, prisons and the police must report anyone voicing extremist views or who is considered vulnerable to radicalisation.
It is part of the overall Prevent strategy, set up after the July 7 bombings in 2005 to tackle extremist ideology.
Last year about 70 per cent of referrals to Channel were linked to Islamist-related extremism and roughly 15 per cent to far-right extremism.
A Home Office spokesperson said: "We have a duty to challenge, at every turn, the twisted narrative that has exploited some of our vulnerable young people. We will continue to work with communities of all backgrounds to challenge those who spread hatred.