High school students at the elite Sidwell Friends School displayed swastikas during an afternoon assembly Wednesday, the head of the D.C. private academy informed families in a letter.

The incident happened during an interactive portion of a presentation about a student-run nonprofit that uses soccer to build community among refu­gee children in the Washington region, according to the letter. The presenter had students use Kahoot, an online game that allows people to build their own quizzes, to answer questions.

Students responded by using their cellphones, and their answers were projected on large screens. But the projections were quickly turned off when an administrator saw that two of the students’ usernames included swastikas. Several other usernames expressed racist views of Asians and Native Americans, according to the letter.

“I am disappointed, dismayed, and deeply sorry that such an incident could take place at our School,” Bryan Garman, the head of the school, wrote in the letter to Sidwell families. “Racism and ­anti-Semitism will not be tolerated in this community.”

Garman said the school has launched a “thorough investigation” to determine the students responsible for the racist and anti-Semitic messages.

HuffPost first reported the incident.

Sidwell is among the most prestigious private schools in the country, educating the children of presidents and powerful Washingtonians for generations. President Barack Obama’s oldest daughter is a graduate, and his younger daughter is a senior. President Theodore Roosevelt’s son attended the school, as did Richard Nixon’s daughters. Bill and Hillary Clinton’s daughter, Chelsea, is a graduate.

Tuition at the Quaker school costs more than $42,000 a year.

This isn’t the first time a swastika has been found at Sidwell this academic year.

Ellis Turner, associate head of the school, said in November that a teacher led an etymology lesson about the naming of the Nazi political party. The teacher did not erase his notes from the whiteboard, and, after the class, someone found a swastika drawn next to the notes.

“We were unable to identify the person who drew the swastika and could not establish the context in which it was drawn,” Turner wrote in an email.

Sidwell is not the only school in the Washington region in which swastikas have appeared on campus.

Last month, a teacher discovered a canopy cut in the shape of a swastika at Mount Daniel Elementary School in Falls Church, Va. Two other swastikas were found in Northern Virginia that same week — one spray-painted onto a drainage tunnel in Fairfax County and another traced with a racial slur into snow in a yard in Loudoun County.

In October, a swastika was found attached to a bathroom wall at School Without Walls, a selective-application public high school in downtown Washington. Administrators at that school had discovered another swastika in the boys restroom in March 2017.

In September 2017, authorities investigated a swastika found painted inside a residence hall restroom at Georgetown University at the start of Rosh Hashanah, the Jewish New Year.