Schools in England have been given the legal right to search pupils who are suspected of carrying knives.
The government hopes to stamp out the use of violent weapons
Head teachers will also be given guidance on how to use airport-style metal detectors to screen young people.
The guidelines state that a pupil can be refused entry to a school if he or she refuses to be screened.
Education Secretary Alan Johnson said knife-carrying in schools was rare, but it was illegal and a message it would not be tolerated must be sent out.
He told the BBC: "What happens at the moment is that if a teacher suspects a child of carrying a knife they have to call the police and wait for the police to arrive before that child can be searched - unless the child agrees to be searched.
"By that time any weapon they are carrying may have been passed on."
Under the new guidelines trained staff, authorised by the head teacher, would be able to carry out searches.
Crucially, a search should never take place where there is any risk to staff or pupils.
They also explain how best to screen pupils, suggesting that randomly selected groups of pupils could be searched in order to send out a strong message of deterrence.
But it also sets out limits for schools, in that suspicion has to be reasonable and not based on stereotypical images of certain groups of pupils.
Two members of staff should be present for a search and both must be the same sex as the pupil.
And students can only be required to remove outer clothing, such as coats or jackets.
Mr Johnson said teachers themselves had asked for the powers but added that the main way to keep knives out of our schools is to continue educating young people about the dangers associated with them.
"I think parents will welcome the clear message that bringing a weapon into school is a criminal offence and will not be tolerated."
But he added: "Let's not exaggerate how our schools look at the moment our schools have a very low proportion with any problem at all with pupils bringing in weapons.
"The Youth Justice Board survey told us that, Ofsted told us that and head teachers and teachers tell her that.
"Lets not exaggerate this into saying our schools are some kind of ghetto from central Manhattan or the Bronx."
National Association of Head Teachers spokesman said it was the job of the police to search individuals for weapons.
"They are trained and have the appropriate body armour.
"Our advice to our members will be to call for police assistance should they suspect that a weapon is being carried."
General secretary of the NASUWT union, Chris Keates, welcomed the new powers, but said searches must be conducted properly by appropriately trained staff.
"However, all schools will still need to consider how they will be incorporated into their policies and procedures to ensure that they are prepared fully should the need arise.
"There is a clear role for local authorities and the local police in supporting and advising schools in this process."
The Teacher Support Network said in the past year its support line had handled 175 calls regarding behaviour management, 30% of which were concerned specifically with violence, abuse and threats.
"Giving teachers facing these issues the power to stop and search pupils may make them feel safer at work though schools must exercise extreme caution," a spokesman added.