The fracas involved an estimated 300 students and prompted school officials to summon police backup. The suspensions were for one to five days depending on the severity of the student's offense.
What began as a peaceful lunch-time protest against Liberty Union High School District's long-standing dress code deteriorated into students hurling plastic bottles of soda across the cafeteria along with salads, pizza slices and chicken rice bowls.
"We were not disciplining for protesting," said Heritage High School Principal Andy Parsons.
Five Brentwood police officers were summoned in addition to the two school resource officers on campus that day, but there were no arrests. No injuries were reported.
Parsons plans to meet today with a group of students who were part of the initial protest to ensure that they understand both the district's dress code and cafeteria rules.
A group of students wearing red clothing -- in violation of district rules that specifically prohibit solid red or blue T-shirts because the colors can signify gang membership -- had gathered in the cafeteria during lunch.
They remained standing in defiance of a rule requiring students to sit down to eat in the cafeteria so that school personnel can monitor behavior more closely.
Those who demonstrated against the dress code claimed that school officials aren't enforcing the rules uniformly.
Although 15-year-old Shamon Cook wasn't part of the protest, she sides with those who were.
"To me, the rule is stupid because it doesn't apply to everybody," she said. "When the white kids walk around here wearing red or blue, they don't get in trouble. It's just being patriotic."
She and her mother both said they don't object to the dress code per se, only that it appears to be enforced selectively.
Melissa Cook said she picks up her daughter from school every day and routinely sees not only white students wearing predominantly red shirts but girls sporting revealing outfits.
"They pick and choose who they're going to let slide," she said.
Although blue and red are colors associated with black and Latino gangs, Parson calls the suggestion that campus employees are singling out teens because of their skin color "absolutely ludicrous."
"It has absolutely nothing to do with race," he said. "There are a lot of kids, so sometimes we miss some. They may feel they're being picked on, but they're not."
The dress code is all about avoiding potentially violent situations in which a bona fide gang member mistakes someone else as a rival gangster, Parsons said.
Most, if not all, school districts in East Contra Costa have adopted general dress codes, although many leave it up to each school to come up with more detailed policies.
"It's not black and white," said Antioch Unified School District administrator Ron Leone.
The districtwide policy doesn't specifically ban red or blue clothing; each campus instead decides what constitutes gang-related attire because the definition changes, he said.
Leone and administrators at other districts in Knightsen, Oakley and Pittsburg said outfits are evaluated as a whole -- whether a red shirt is worn along with other articles of red clothing, for instance, as well as how often it's worn and whether the student associates with a group of similarly dressed teens.
Reach Rowena Coetsee at 925-779-7141.