Headmasters and teachers at Britain's privately owned and state-run schools have been ordered to be on the lookout for Muslim extremists attempting to "groom" youngsters to their cause.
The new legal requirement comes after terrorists killed some 30 British tourists at Sousse, one of Tunisia's best-known holiday resorts, on Friday.
It was the worst terrorist attack against Britons since 2005, when 52 people were killed in a series of bomb attacks in London.
In a statement, the British government explained that no military action would be taken without the permission of Parliament.
But Prime Minister David Cameron said another kind of war is underway -- one aimed at making the British public "more intolerant of intolerance."
Cameron told MPs on Monday: "We will not give up our way of life or cower in the face of extremism. This is not the war between Islam and the West, which [ISIS] wants people to believe. It is a generational struggle between a minority of extremists, who want hatred to flourish, and the rest of us, who want freedom to prosper."
New guidelines that will come into force this week will require public bodies such as city councils, schools and prisons to take responsibility to prevent the spread of terrorism.
Employment checks will be devised to bar extremists from working with children.
To prevent a form of Shariah, or Islamic law, from taking root in parts of England, police chiefs will be ordered to ensure that Muslim communities do not operate parallel justice systems.
"We must take on the radical narrative that is poisoning young minds," Cameron said. "The people who do these things do it in the name of a twisted and perverted ideology which hijacks the Islamic faith and holds that mass murder and terror are not only acceptable but necessary."
