The school is known as the Indians, and has a logo with a Native American wearing a bandana with a feather.
Indigenous groups complained the mascot dehumanizes Native Americans.
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Last month a committee of students, alumni, and faculty and school board members recommended changing it.
The school board will discuss that committee's recommendation Thursday evening.
The rally will be held at 4 p.m. before the 6 p.m. meeting.
A final decision is expected in two weeks.