The free period is a prime time for clubs to meet and for kids with packed schedules to make up tests, projects and labs.
But that won't be possible with club members divided up and teachers in session during lunch, students say. The change proposed by administration will rob them of those valuable 36 minutes, they say.
"We can't have this. This just jumped out at us," said junior Connor Donnelly, who organized the rally through his Facebook account, an online social networking site.
Students on campus last Friday afternoon met in front of the school, some chanted and others just stood with their arms around each other. More than 600 students have signed a petition to oppose the split lunch.
Principal Becky Smith said the school needs to look into dividing the lunch period because its projected enrollment exceeds capacity. It's too hard to regulate the closed campus with over 2,400 kids out of class at once, she said.
"It almost becomes crowd control as far as safety," she said.
But Donnelly and his throng of teenage demonstrators say breaking students apart could stir up a new set of problems.
"You're gonna have kids cutting class to hang out at lunch," Donnelly said, explaining that most students are upset about the proposal for social reasons.
In coming weeks, the school will gather surveys from students and get parent and teacher input. That will include feedback from the site council and a survey given to students during class.
Donnelly, who has athletics after school, said without one lunch period for all, his global warming prevention club will likely have to meet around 7 a.m.
Some of the club's members have an early period. Others have sports or jobs after school. And getting up that much earlier is just not something a bunch of sleep-deprived teenagers are willing to do, he said.
"The clubs are going to fall out," he said.
Even teachers are divided on the subject. The proposal makes for a less chaotic free period, they say. But it's also another hurdle to jump when it comes to finding times to give students extra help, rehearsing and allowing make-up work.
Eighteen-year Monte Vista speech teacher David Matley said he supports the proposed double lunch even though it's inconvenient for speech and debate meetings. The student population is "simply too big to supervise during a single period," he wrote in an e-mail this week.
"It is a big change, but when you consider the size of the lunch lines and the crowded hallways, I think the students will be happy in the long run," he said.
Smith said she expects students will be able to solve their scheduling conflicts, should the split lunch be adopted.
"Our kids are pretty creative about coming up with solutions to problems," Smith said.
A decision will be made by the end of the year, using data from six other schools, along with the statewide Healthy Kid's Survey.
For now, Donnelly hopes that "one thousand kids walking up in a sea of white" is feedback enough - at least on where students stand.