Schools were told today that they do have the power to confiscate mephedrone from pupils - despite it not being banned under the law.
Fears were raised earlier this week that teachers were unable to seize the drug, which has exploded in popularity in the last year.
But Schools Minister Vernon Coaker has written to every school in England telling them they can seize mephedrone and all other "legal highs" under existing rules.
Known as Meow Meow or M-Cat, mephedrone has effects similar to those of ecstasy. It has been linked to the deaths of two teenage boys, Louis Wainwright, 18, and Nicholas Smith, 19, in Scunthorpe.
Mr Coaker said the law gives teachers the powers to confiscate "all inappropriate items" irrespective of their legal status.
Schools are also under no obligation to return confiscated substances, he said.
Mr Coaker wrote: "Some questions have been raised as to whether teachers can confiscate such substances, given that they are not prohibited substances.
"As current guidance makes clear, schools do have the power to confiscate inappropriate items, including a substance they believe to be mephedrone (or any other drug whatever its legal status) in line with the schools behaviour policy.
"They do not have to return such confiscated substances."
Along with the letter, schools were also sent a factsheet containing advice for staff on the dangers of mephedrone.
The leaflet warns that mephedrone users can suffer anxiety attacks, paranoia and nosebleeds. The drug can also cause fits, and has been linked to "a small number of deaths", it states.
The dangers of mephedrone are being examined in detail by the Government's drug advisory body, the Advisory Council on the Misuse of Drugs (ACMD).
Conclusions will be presented following a meeting of the council on March 29 and ministers have pledged to take "immediate action". But a ban is unlikely to become law until the summer.
Critics said the delay was the fault of Home Secretary Alan Johnson, who sacked the former head of the ACMD, Professor David Nutt, last year.
As a result of the sacking, other committee members resigned, slowing down work on the drug, it was claimed. But ministers denied there was any "inordinate delay".
Earlier this week, Mike Stewart, headmaster of Westland School in Torquay, told the Telegraph his teachers were forced to hand back bags of the stimulant seized during lessons.
He said: "Both my colleagues in school and the police are pretty powerless to do anything about it.
"Obviously items can be confiscated but, because this is still legal, it would have to be given back at the end of the day, and that's disturbing," he said.
"It is a widely available unrestricted drug. It has significant harmful effects on the behaviour of young people and probably their future lives."