The billboard in West Modesto on Maze Boulevard states, "Intoxication Leads to No Graduation."
A student group called Friday Night Live used grant funds to put it up.
"They're big and they're out there and people can see them," said Taylor Tran, a junior at Modesto High School. "We wanted something big and quick that will catch people's attention."
The teens say they know underage drinking is an issue and found that the billboard, among other initiatives they're working on, could be a creative way to warn peers and parents.
The group has adult mentors but for the most part the teens brainstorm and come up with ideas on their own.
Felix Hernandez said he's overheard students talk about the project already.