CHICAGO (CBS) — A west suburban school reopened Friday morning, after it was closed for disinfection because dozens of students had come down with stomach flu.

Officials at Robinson Elementary School in Lyons said 80 students absent on Wednesday – including kids who called in sick, went home sick in the middle of the day, or had their parents pick them up for a doctor’s appointment.

That’s nearly a third of the school’s student body of 260 children, so the school canceled classes on Thursday to disinfect the building. It took custodians 20 hours to clean the building with bleach.

“Everything got a deep cleaning. Everything was wiped down; from doorknobs, to tables, to toys,” said Dr. Mary Jo Vladika, superintendent of Lyons School District 103.

Another 20 students and 8 staff members called in sick Friday, when classes resumed, but the rest were back in school, and happy to be there.

Guillermo Vazquez’s 5-year-old son was one of the 80 students who missed school Wednesday, because of the stomach flu.

“He started three days ago. … Throwing up, fever, he didn’t feel good,” Vazquez said.

After a few days at home, his son was healthy and back in class, but now his younger brother has caught the bug.

Their 10-year-old sister, Frida, said she managed to stay healthy when both her brothers got sick, because “I didn’t get close to them.”

Parents were happy the school decided to close for a day to disinfect the building, and protect other students.

“I feel good, since they closed the school to disinfect everything,” Christina Chavez said.

Fellow parent Anna Dimas said she hopes parents are smart enough not to send their kids to school if they’re sick.

“There’s other kids at risk, too, that could get sick,” she said.

Crews will do a similar cleaning Saturday at Washington Middle School, in case older siblings of Robinson students bring the bug with them there.

Officials said the flu scare at Robinson is a reminder of the importance of being immunized against seasonal flu.

The Illinois Department of Public Health said, while most patients recover from the flu in one to two weeks, influenza and pneumonia have killed an average of 3,500 Illinois residents a year over the past decade.

Those at greatest risk of serious complications from the flu are the very young, the very old, and the chronically ill.