As students head back to Iowa schools, the number of children age 17 and under who tested positive for COVID-19 has grown by 411 in the last three days, according to public health data released Sunday morning.The increase brings the statewide total for that age group to 6,380.While younger children appear to be less vulnerable to complications from the infection, public health officials have expressed concern they could spread the disease to people who are — such as teachers and older family members.The number of people in education as an occupation who have tested positive grew 254 in same three days, for a total of 3,080, the data show.Iowa surpassed having 80,000 total COVID-19 cases in the last six months with the addition of 874 new cases in the 24-hour period that ended at 11 a.m.