High-school students at one of the country’s most elite schools projected swastikas on a screen at an afternoon assembly Wednesday, The Washington Post reports. The head of Sidwell Friends School informed families about the incident in a letter, saying he was “disappointed, dismayed, and deeply sorry.” The incident happened during an interactive section of the assembly during which students’ usernames were displayed on the screen. An administrator saw two of the students’ usernames included swastikas while others expressed racist views of Asians and Native Americans. Head of School Bryan Garman wrote in the letter to Sidwell families: “Racism and anti-Semitism will not be tolerated in this community.” The school has now launched a “thorough investigation” to determine who was responsible. Tuition at the Quaker school costs more than $42,000 a year—its alumni includes President Barack Obama’s daughters, Sasha and Malia, as well as Chelsea Clinton and Richard Nixon’s daughter Tricia.