A student who cut her leg at Hillcrest High School in Hamilton sparked a medical emergency as the school nurse had to stem the flow of blood.
The school was in lockdown this morning for half an hour as teachers dealt with the medical emergency shortly before interval.
The lockdown has now been lifted, although the school is still waiting for an ambulance.
The 1800-student school was put into lockdown about 11am, according to its Facebook page but the lockdown has now been lifted.
Deputy Principal Ronan Bass says it was standard procedure to put the school in lockdown in such circumstances so 1800 kids were not running about while St John Ambulance helped the student.
Principal Kelvin Whiting told the Herald the accident happened in a main thoroughfare and the Year 10 student needed to be stretchered to the sick bay.
He said the student cut her lower leg but it's not yet clear how.
"It was serious enough that we had to stabilise her in terms of bleeding. Then we rang for the ambulance and put the school into lock down which means we could treat her. The staff and nurses did a great job."