Those at the rally waved large American flags and carried signs saying things like, "Free the freedom of speech" and "I'm sorry if this flag offends you."
The signs took aim at the controversy that erupted on Cinco de Mayo when five students were sent home after refusing to turn their shirts inside out.
"There's tons of people here and we love our country, and we want to make sure everyone has a right to free speech and to have the American dream," Denise McElhiney told ABC7.
The Live Oak High School principal issued an apology to the school and the community because the students were asked to leave the campus.
The administration says they took the action as a preventative safety measure, thinking the shirts might spark a confrontation on a day when Latino students celebrated the Mexican victory over the French in 1862.