CASCADE, Idaho -- School has been canceled for the rest of the week in the Cascade School District after a severe flu outbreak sickened nearly one-third of students.

Superintendent Pal Sartori said flu has been affecting staff and students for several weeks, but attendance took a nosedive this week. Classes were canceled for Thursday and Friday.

"I've been at the school for 27 years and this is the first time we've had to close because of illness," Sartori said.

The superintendent said that about 23 percent of students were absent Wednesday, but the number of kids who were actually sick was higher - totaling more than 30 percent of the district's approximately 230 students.

School rules mandate that students who did not attend class can not participate in that day's sports or extracurriculars, leading some students come to school even though they were sick, he said.

"We had a lot of people walking the halls who were coughing and hacking just because they didn't want to miss their extracurricular activities - basketball practice, basketball games, things of that nature," Sartori said.

Satori said district officials also checked in with the local clinic, where health workers told them they had never seen such a high number of people coming in at once with issues related to flu, pneumonia and bronchitis.

"In a small school district, we felt like we would most likely have to reteach everything," he said. "We felt it was best to shut it down and hopefully give them an opportunity to go home and get themselves healthy and come back on Monday the 29th."

Because the school district has extra days built into the calendar, students and teachers will not have to make up the sick days at the end of the year.

Parents and the school board supported the decision to cancel school, Sartori said. The school will be sanitized before the K-12 students return on Monday.