The parents of a sixth form pupil at Ilkley Grammar School have won an appeal against the decision to exclude her from the school for possession of a small amount of cannabis.

The 16-year-old, who has not been named, was excluded informally by the Cowpasture Road school in January after being found in possession of the class C drug while on its premises.

When her parents said they wished to appeal the decision, the Year 12 pupil was formally excluded to allow an appeal hearing to take place.

A panel of school governors upheld the exclusion at a hearing in February but that decision has now been overturned by an independent appeal panel sitting at Bradford's City Hall.

The pupil's father said: "My faith in the appeal system has been partly restored. While I do not agree with anybody using cannabis, pupils should not be permanently expelled for a first-time offence or possession of a minute quantity.

"A high proportion of young people experiment with cannabis. Expelling them from school as an example does not help anyone. In most cases, it just makes the wider situation worse, including that of the schools.

"I am currently looking at the possibility of a civil claim against the school for unlawful exclusion."

James Wilson, a solicitor with Huddersfield-based firm Ridley & Hall, represented the pupil and her family at the appeal hearing. He said: "The decision to exclude the pupil for possession of a minute amount of cannabis was irrational.

"The reason behind the exclusion appears to be that the head teacher was angry that other pupils circulated a petition to try to keep the pupil in school. Clearly it is not rational to expel one pupil for what other pupils have done."

School head teacher Gillian James said: "We do not have an ongoing drugs problem in our school. Any decision to permanently exclude a student is not taken lightly, balancing the nature of the disciplinary offence and the interests of the excluded student with the effect on the school and its students.

"The Department for Children, Schools and Family drugs guidance states: it is important for schools to reinforce to pupils the message that cannabis is harmful to health and is an illegal drug, and that possession remains a criminal offence which may lead to a criminal conviction'.

"Our Drugs in School policy states that our intention is: to send a clear message that drugs, drug takers and drug dealers have absolutely no place in school'."

The pupil will begin her A-level studies again at a different school from September.