The U.S. Education Department said it is investigating Denver Public Schools for alleged discrimination after the district converted a girl’s restroom on the second floor of East High School into an all-gender restroom while leaving the other bathroom exclusively for male students.

The probe comes after President Donald Trump repeatedly promised on the campaign trail to drive what he called “transgender insanity” out of schools.

Denver Public Schools called the decision to investigate the conversion of a women’s restroom into an all-gender facility as potential discrimination “unprecedented.”

An all-gender restroom at East High School in Denver is the subject of an investigation launched by the U.S. Department of Education.

The federal Education Department says the move may violate Title IX, which prohibits discrimination on the basis of sex.

The U.S. Department of Education released a letter on Tuesday accusing Denver Public Schools of discriminating against female students with this facility.