Yap Zong Yao woke up at 5 a.m. Saturday in Singapore to check his admissions decision from Vassar College. He returned to sleep “overwhelmed with joy,” he said.

Mahmoud Ghedira stayed up with family members until 11 p.m. Friday in Tunisia as they toasted the son who had impressed an esteemed American school.

Megan Curiel, from San Antonio, saw the good news on her iPhone and sobbed. Her father called relatives. She ordered two Vassar sweatshirts — one for her and one for her mother. They popped Champagne.

“I was in,” Ms. Curiel said, “for about three hours.”

About 4 p.m. Friday, Eastern time, scores of early-decision applicants to the college, in Poughkeepsie, N.Y., were mistakenly told they had been accepted, the school said.