Image caption Some companies and organisations routinely test staff for drugs

Teachers at an independent special school in Derbyshire are on strike after one of them was asked to take a random drugs test.

Eleven teachers at the Alderwasley Hall School, which is a residential centre as well as a school, are taking action this week.

Their union, the NASUWT, says one teacher was suspended after refusing to take a test, although this was lifted late on Wednesday.

The school is not commenting.

The union says other members of staff have been threatened with dismissal if they refuse to take a test.

Chris Keates, the general secretary of the NASUWT, said: "It is simply unacceptable for an employer to impose a policy of drug and alcohol testing which we believe is unjustified and unlawful and attacks the professionalism of the teachers at the school.

"There is no basis whatsoever for believing that dedicated and committed teachers at Alderwasley Hall School are misusing drugs or alcohol.

"This is simply a case of an employer abusing its position and flagrantly disregarding the rights of its employees."

Employees in certain roles, including those involving safety or care of other people, are sometimes asked to take part in random drugs tests and some US schools run drugs tests on students.

Government guidelines say employers have to have consent from staff they want to test for drugs and that tests should be random.

Human rights legislation

In this case, the union says the company that runs the school, Senad, brought in a policy of random drugs testing of staff in January 2009 and later that year asked staff to sign new contracts that had a clause agreeing to random urine and blood tests.

The union says its members refused to sign the contract but there were no requests for drugs tests until last week.

They have been on strike since Tuesday this week, but the school has remained open, because teachers make up a small proportion of the staff there.

The union says the school's policy on drugs tests is unlawful under human rights legislation because it allegedly breaches a person's right to respect for their private life.

There are exceptions in law where public health and safety is at stake, but the union argues these do not apply in this case.

The school and Senad group have been contacted by the BBC but did not wish to comment.

In state schools in England, teachers have the power to search pupils for drugs if they give consent, government guidance says.

The guidelines add: "The Association of Chief Police Officers (Acpo) recommends that drug dogs and drug testing should not be used for searches where there is no evidence for the presence of drugs on school premises.

"However schools may choose to make use of drug dogs or drug testing strategies if they wish. It is advisable that the school consults with the local police."