The youngsters are among more than 750 children of school age who have been reported to the authorities because of worrying behaviour.
It includes drawings of bombs and alarming messages as well as associating with suspected fanatics.
The children have all been referred to the Channel project, which is run by the Home Office and Association of Chief Police Officers (Acpo) and designed to stop vulnerable people being drawn in to extremism.
A total of 2,653 referrals, of both adults and children, have been made since the scheme was launched in the wake of the July 7 suicide attacks in 2005.
Those reporting individuals include teachers, parents, youth workers, neighbours and even bin men.
The majority of referrals involved concerns over vulnerability to Islamist extremism but almost 400 cases involved far right radicalisation.
Police leaders last night said the project, which has been gradually rolled out nationally, is now recognised as a vital tool in protecting communities.
It is also seen as all the more important amid the growing terror threat from so-called “lone wolf” fanatics who radicalise themselves over the internet.
However, civil liberty groups have warned the project encourages people to spy on their neighbours.
The Channel project was set up following the 7/7 attacks where “home-grown” suicide bombers killed 52 innocent people on the London transport network.
The aim is to identify people vulnerable to extremism and involve appropriate agencies to address their behaviour and keep them away from danger.
It can include work with schools, social services, police, health and local councils.
In the first pilot year in 2006/07, just five people were referred but some 748 were reported last year following the national roll out.
Of those, 645 were aged 12 to 16 and another 113 were aged under 12, according to figures obtained under the Freedom of Information Act.
In one case, a three year old child was involved because an entire family was referred.
An Acpo spokesman said: “This is a very rare occurrence in which it was felt that Channel was the best support mechanism to safeguard the child and that it was necessary to enable the family unit to benefit from the expertise and wrap around support that Channel provides.”
Previous cases have included a teenage schoolboy in East Lancashire who was referred for regularly drawing bombs and guns.
Another youngster wrote “I want to be a suicide bomber” in a school book.
Others reported were new neighbours behaving oddly, including keeping their curtains shut, a bus passenger expressing racist views and a vulnerable loner who suddenly gained new friends. The police chose to take no further action in those cases.
Of the 2,653 referrals, 67 per cent was associated with Islamist extremism and 14 per cent, or 371 cases, involved far right extremism, including evidence of swastikas.
Police and other agencies took further action in 587 cases after assessing the individuals were vulnerable.
Deputy Chief Constable Craig Denholm, the ACPO lead on Channel, said: “Channel supports people who are vulnerable to being radicalised and drawn into terrorism.
“It works in a similar way to other safeguarding, partnership activity where agencies come together to support vulnerable individuals; for example work to address drugs, guns and gangs issues through early intervention.
“Types of support can include life-skills, mentoring, and access to education, careers advice, and consideration of housing need amongst others.
“It has increasingly become recognised by partner agencies as having an important role to play in safeguarding communities from harm.
“Both vulnerable adults and young people are safeguarded through Channel.
“In exceptional circumstances some younger children are provided support as part of a wider, whole family approach.
“This does not mean that a young child is expressing radical views. However, this enables a family to benefit from the expertise and wrap around support that Channel provides.”