Those numbers have risen every day this week, reaching 90% as of Thursday, officials added.
CPS said those numbers reflect "the result of months of hard work" to engage and encourage CPS families to take the steps needed to prepare for the return of virtual school.
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The first-day number is 10% lower than the first day of school attendance the previous three years, according to CPS.
"While our first-day attendance rate is lower than in-person school comparisons due to challenges related to the ongoing COVID-19 pandemic, I am encouraged by our outreach efforts, which will remain ongoing as we work to ensure families have what they need to participate in remote learning," said CPS CEO, Dr. Janice Jackson.
FULL CPS SCHOOL-BY-SCHOOL 1ST DAY ATTENDANCE RATES
While CPS officials touted the week's attendance rates, some individual schools' figures appear to be extremely low.
Network 11 schools (Englewood, Auburn Gresham, Washington Heights) have the lowest average attendance at 65.44%.
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The district says they will be sending security officers out next week to get in touch with students who have not logged in yet this year.
CPS classes began on September 8.