A Native American student sued his California school district on Monday over its refusal to let him wear an eagle feather during his high school graduation ceremony, claiming his rights to freedom of expression and religion in the state constitution are being violated.

Christian Titman, 18, a member of the Pit River Tribe, said he wants to attach the 5-inch feather from his father to the tassel on his cap at the Clovis High School ceremony set for Thursday.

He wants to mark his achievement and honor his Native American heritage, according to the lawsuit filed in state court in Fresno County. The tribe considers eagle feathers sacred and symbolic of a significant accomplishment.

"The district's refusal to allow a small symbol of religious expression during the graduation ceremony is a misunderstanding of both the spirit and the letter of the law," said Novella Coleman, a staff attorney with the American Civil Liberties Union of Northern California, one of the groups representing Titman. "The implication that an eagle feather with religious significance is unacceptable or disruptive signals a deep disrespect from the district."

A call to the district was not immediately returned.

But in a letter to Titman's attorneys, Superintendent Janet Young said the district has a strict graduation dress code that was intended to show "respect for the formality of the graduation ceremony, unity of the graduating class, and also to avoid disruption of the graduation ceremonies that would likely occur if students were allowed to alter or add on to their graduation cap and gown."

Young said the district has previously refused to allow stoles, leis, rosaries and necklaces on graduation caps and gowns, and its dress code is neutral to any religion. She said Titman could wear the eagle feather after the ceremony and take photos with the principal.

Titman is seeking a court order that would allow him to wear the feather as well as a declaration that the district cannot prohibit religious symbols or insignia at graduation. Titman's attorneys have asked for a hearing on Tuesday, two days before the graduation.