In a high school lobby in New Jersey, the principal saw a student heading toward a stairway and moved to cut her off. There was physical contact between them, though no blows.

The interaction lasted less than a minute.

The student filed an affirmative action complaint against the principal, saying that he had grabbed her and “slammed” her against a wall. The student is Black; the principal is white and Latino.

The principal, reporting the episode later that day, said he was preventing an…