St. Ignatius College Preparatory in San Francisco’s Sunset district reopened today after being closed for three days last week because of a stomach virus, said school officials.

The virus sickened more than 300 students and 30 teachers, Principal Patrick Ruff said.

The high school, located at 2001 37th Ave., was shut down on Wednesday because of an outbreak of gastroenteritis.

Fifty students had called in sick on Tuesday, and another 90 were sent home that day, many of whom had vomited in trashcans or in bathrooms on campus, Ruff said.

The campus underwent a deep cleaning, and the city’s Department of Public Health cleared classes to resume on Thursday, but school officials decided to keep St. Ignatius closed until today “to ensure the health of our students,” Ruff said.

Dr. Tomas Aragon, the Department of Public Health’s director of population health and prevention, said the extended closure was wise, in part because it would be difficult logistically to hold classes with so many teachers out sick.

In addition to the campus closure, several of the school’s sports teams had games postponed because of the outbreak, including the boys’ and girls’ basketball and soccer teams, Ruff said.