It was a jarringly mediocre report card for Ms. Kagan, and the torts grade in particular came as a shock to her and to her friends, recalled Jeffrey Toobin, the legal affairs writer for The New Yorker and CNN, who was in Ms. Kagan’s study group. He attributed the result to a “bad day in the exam.”

Image Elena Kagan got marks that were low — for her — in her first term at Harvard Law. Credit... Doug Mills/The New York Times

“She was definitely upset about this torts grade — there was no doubt about it,” Mr. Toobin said. “I remember saying to her that in the larger scheme of things it will not loom very large, and I would say history has vindicated me on that matter.”

Ms. Kagan soon returned to her habitually high level of academic accomplishment: her spring semester report card in 1984 consisted of three A’s and an A-minus. She went on to become supervising editor of the law review, graduate magna cum laude, and clerk for an appeals court judge and a Supreme Court justice, Thurgood Marshall.

Indeed, a transcript she submitted with her application to Justice Marshall, which is included with his papers at the Library of Congress, shows she earned A’s in 17 of the 21 courses for which she received a letter grade. In two more — including an administrative law course, a field in which she would later focus as a scholar — she earned a B-plus.

Among several recommendation letters from her professors, one, from Frank I. Michelman, urged Justice Marshall not to be dissuaded from taking her on because of those lower marks. He noted that he had taught Ms. Kagan during her first term at law school — a full-year course in property law that did not give grades until the end of the spring term. He gave her an A for the entire year’s work.