As a Long Island high school student checked her phone for the results of her college admissions applications, she was overcome by disbelief.

One by one, each relayed the same news: Harvard. Yes. Dartmouth. Yes. Princeton. Yes. The University of Pennsylvania. Yes. Cornell, Yale, Columbia, Brown: yes, yes, yes, yes.

It was March 31, the emotion-filled day when Ivy League universities posted their decisions online. And Augusta Uwamanzu-Nna, a senior at Elmont Memorial High School, became the second student there to pull off an exceedingly rare feat: She swept all eight.

She screamed. Then she cried.

“It’s so surreal,” Ms. Uwamanzu-Nna, 17, said on Wednesday. “It’s still hard to actually believe that this has happened to me.”