About 22% of boys aged 14 and 15 have carried weapons in Guernsey, a survey by the Education Department revealed.
Nearly a quarter of Year 10 boys said they carried a weapon
About 2,000 schoolchildren aged between 10 and 17 took part in the online Bailiwick of Guernsey Young People's Survey 2007 earlier this year.
Most pupils said they felt safe or very safe from physical or property crime, although one third of pupils said they had been bullied.
The survey of about 100 questions aimed to reveal behaviour and attitudes.
The survey showed 22% of Year 10 boys said they carried some form of weapon sometimes, usually or always.
Another 22% of Year 6 pupils reported being approached by an adult who had worried them or made them upset.
About 90% of pupils said they had mobile phones and access to the internet.
There was a decrease in the numbers of pupils who had taken drugs since 2002.
The numbers of pupils who had smoked had declined and numbers of pupils who had drunk alcohol in the past seven days had increased significantly.
Despite 77% of pupils falling within the average band of body measurement classification, a significant number of girls wanted to lose weight.
Alun Williams, Guernsey's Lifelong Learning Manager, said: "This will inform our work with young people over the coming years."
An Education Department spokeswoman said teachers would be using the data from the survey to help shape their Personal, Social, Health and Citizenship Education programmes.