hanna, albertaStudents writing a chemistry final at a high school in Hanna, Alta., northeast of Calgary, instead got a quick lesson in anatomy on Friday from a streaker.

About halfway through the provincial diploma test a boy shouted, "Grad 2011," as he ran through the exam room naked, except for a rubber mask over his head.

After that, it was hard to concentrate, said student Aly Price.

"Me and my other friend that was writing her chem too, like we both, like our minds went totally blank after that. And so hopefully that doesn't affect us with our marks," she said.

The young man was caught and has been charged, the school's principal said.

It will be up to the province's Education Department to decide if any of the students can re-write the exam because of the disruption.

Hanna is about 215 kilometres northeast of Calgary.