US school students have been armed with rocks to protect themselves from school shootings.
The cunning plan was announced by Pennsylvania's Blue Mountain School District superintendent David Helsel.
"Every classroom has been equipped with a five-gallon [19-litre] bucket of river stone," he told lawmakers at the capital city of Harrisburg last week.
"If an armed intruder attempts to gain entrance into any of our classrooms, they will face a classroom full of students armed with rocks and they will be stoned."
Mr Helsel said the genius idea just came to him one day.
"At one time I just had the idea of river stone - they're the right size for hands, you can throw them very hard and they will create or cause pain, which can distract," he said.
Teachers, staff, and students in his district have been given active shooter training. If a teacher decides to lockdown a classroom, the rocks are a last resort.
"We have devices installed in our doors that help to secure them, to make it very difficult to break through," Mr Helsel said.
"We also have - we train kids and talk about barricading the doors."
Parents have described it as a "creative idea".