Denver Skey has changed his plea from not guilty to guilty.
The 18-year-old is charged with two counts of uttering threats to cause death or bodily harm, stemming from an incident that led to the evacuation of the school and the cancellation of the Mount Sentinel graduation ceremony in June.
Skey is due in Nelson court on Monday, when the judge will ensure that various pre-sentence reports will be ready for sentencing, which is currently set for December 28.