A letter addressed to the superintendent from 12 community groups — including the American Civil Liberties Union of Idaho, Planned Parenthood and Immigrant Justice Idaho — said that “the school and community climate in Idaho continues to grow more harmful against specific groups and identities, including our Latinx friends, family and neighbors.”

“The intent or misjudgments of the individuals involved does not undo the trauma experienced by students, families and communities,” the letter said.

Middleton, Idaho, is a city of 7,400 just over 20 miles northwest of Boise. During the 2015-16 school year, about 12 percent of students at Middleton Heights Elementary School were Hispanic, according to the National Center for Education Statistics.

It was unclear why the employees dressed up the way they did. Two parents who visited the elementary school on Halloween, and who spoke only on the condition that their names not be used for safety reasons, said the faculty was having a costume competition where groups of teachers dressed up to represent various countries.

State education officials said complaints — and any possible disciplinary or corrective action — would be handled by the local school board. Dr. Middleton and other school district officials, including board members, did not respond to requests for comment.

J.J. Saldaña, who oversees education efforts for the Idaho Commission on Hispanic Affairs, a state agency that serves the Hispanic community, said Friday that he had been inundated with calls from upset parents and community members.

“My phone has been ringing off the hook all day,” said Mr. Saldaña, who said he was collecting letters from community members.