Class will be back in session this morning at Robinson Elementary School in Lyons which closed Thursday when a third of its students got sick.
The school has been scrubbed by a cleaning crew.
Officials say four or five students at a time started coming into the office with flu-like symptoms.
When staffers also started going home sick, the school contacted the Cook County Health Department.
Health officials say it was probably norovirus, which is very contagious.
Nearby Washington middle school was also cleaned, because many Robinson students have siblings there.