Three students from Southern Cross Campus, in south Auckland, filmed themselves live on Facebook smoking weed from soft drink cans inside the school grounds.

The footage shows the three boys, wearing their Southern Cross Campus school uniforms discussing what they're doing while filming themselves preparing the weed and then smoking it from a Mountain Dew can.

The boys smile and crack jokes while they share the can. The boy sitting in the middle, who uploaded the footage to Facebook, shows off the drug in front of his cell phone.

"Look at these mean buds," he says.

The nearly 3-minute long video was broadcast on Facebook on Thursday afternoon with the caption "having a stoney".

Southern Cross Campus principal Robin Staples told the Herald the school is aware of the video and is "very disappointed".

"This does not reflect the school's principles," he said.

Staples says the school is addressing the issue as a matter of urgency and the boys will be subject to "very serious discipline".

"More likely they'll be suspended and have to report to the board of trustees."