Pupils who have carried out anthrax hoaxes in schools are facing up to 15 years in jail after a spate of scares.

Most incidents have been chalked up to panic and no anthrax has been discovered in a school. But officials are cracking down on students who play hoaxes in a time of acute national anxiety.

“A school, in the eyes of a terrorist, makes a prime target because it reaches the very jugular vein of our emotions - our children,” says Curt Lavarello, director of the National Association of School Resource Officers. “We now realise, as a society, how vulnerable we are.”

Anthrax bacteria in the mail has killed at least three people in the US and infected dozens of others. It caused chaos in the heart of government after it was detected in the Capitol building in Washington.

But most of the incidents in schools have been hoaxes, and government officials have imposed unusually severe penalties.

A 17-year-old Florida student allegedly spread headache powder on a teacher’s desk in the hope that classes would be cancelled. He was suspended and charged with a felony punishable by up to 15 years in prison and a $10,000 fine.

A 15-year-old in Florida was sent to a juvenile jail after composing the message “Anthrax is here and in this school, bye now” in a typing class. He also faces up to 15 years in prison.

In Louisiana, a 17-year-old student spent a night in jail after allegedly pouring correction fluid on his desk and telling a teacher it was anthrax.

In New York, white powder fell out of an envelope and onto the hands of a teacher in an elementary school, causing the students to panic and run out of the building. That instance, too, was considered to have been a hoax.

Even a teacher has been accused of an anthrax prank. A 39-year-old science teacher was arrested after filling an envelope with a white powder and trying to mail it from her school in Ohio to her brother in what the teacher herself later said was “a sick joke”.

She was suspended from her job.