Flyers are seen posted on a college noticeboard on campus at Yale University in New Haven, Connecticut November 12, 2015. More than 1,000 students, professors and staff at Yale University gathered on Wednesday to discuss race and diversity at the elite Ivy League school, amid a wave of demonstrations at U.S. colleges over the treatment of minority students. REUTERS/Shannon Stapleto

(Reuters) - A Yale University instructor whose open letter suggesting that students had a right to wear even offensive Halloween costumes set off a wave of campus protests about racism has resigned, the school said.

Yale was one of dozens of U.S. colleges and universities where students protested this fall about the legacies of racism on campus. The wave of demonstrations led to the resignation of the president of the University of Missouri and promises at Ivy League schools including Yale and Brown University to boost the resources they commit to promoting diversity.

Yale instructor Erika Christakis drew protests after she responded to a university missive urging students to avoid Halloween costumes that could be construed as offensive with an email saying students have a right to be “obnoxious.”

New Haven, Connecticut-based Yale said on its website late Monday that Christakis, was “highly valued and she is welcome to resume teaching anytime at Yale, where freedom of expression and academic inquiry are the paramount principle and practice.”