It’s one of the biggest nights of their young lives — and one Toronto high school is making sure they don’t drink it away.

Students from Malvern Collegiate Institute arriving for their prom Friday will be required to take a breathalyzer test before gaining admission. If any alcohol is detected, the student won’t be allowed in.

“It’s necessary because they’ve had incidents in the past, and the parents and the teachers, and generally the community said enough’s enough, we’re not going to have our prom spoiled anymore,” said Sheila Cary-Meagher, Toronto District School Board trustee for the ward that includes the Malvern school.

“There may be one or two people who find it offensive but by and large, it means that they have a much nicer dance,” she said.

The school, located on Malvern Ave. in the Upper Beaches, has had the test on-hand at the end-of-school dance for the last nine or 10 years, said Ryan Bird, spokesperson for the school board.

It’s is also not the only school to use breathalyzers, he said, adding that one has had it on hand in the past and not even used it.

“A general rule across the board is if you’ve been drinking, you’re not allowed in. That’s nothing new. But the breathalyzer is an added option that they chose to use.”