Mount Hutt College students will be allowed up to eight cans of five percent or less alcohol at their after-ball this month.
There's concern in the region around teenage alcohol abuse, after a parent complained in March when three students were suspended after being found intoxicated.
Ashburton's Community Alcohol and Drug Service says tighter measures have been put in place, including limiting students to the eight cans.
Service manager Chris Clark says parental supervision and security will also be stepped up.
"Working with them and planning a safe event and having some alcohol management plan so that we've strategies in place to A, prevent, but also to deal with any issues that come up on the night."
Mr Clark says there are only two after-balls in the town and she helps with both.