MILWAUKEE (CBS 58) -- Do masks make a difference in schools? Since the first day of school, CBS 58 morning anchor Mike Curkov has been tracking COVID cases in 16 southeast Wisconsin school districts as reported by each districts' online COVID dashboard.

These are daily snapshots of then-current COVID cases taken each Monday morning.

Using that data, we've created a graph showing the percentage of enrollment in isolation with COVID-19 from the beginning of the school year through Monday morning, Feb. 14.

Data seems to indicate that masks were making a difference before Omicron began to dominate our area in December. The difference, on average, between mask-required districts (greens) and mask-optional districts (blues) appears to be clear. However, none of the districts we followed ever rose above a 2% positivity rate until December-January.

Once Omicron hit, masks appeared to make little difference. In fact, many of the mask-required districts had a higher percentage of cases than mask-optional districts.

The second graphic shows the timeline of the raw number in each of the 16 districts. As expected, the larger districts usually had the highest numbers with certain exceptions. At different times, Mukwonago and Oconomowoc had high numbers compared to similar-sized districts.

Data is from the following school districts: Waukesha, West Bend, Wauwatosa, Oconomowoc, Oak Creek-Franklin, New Berlin, Mukwonago, Cudahy, Grafton, Burlington, Whitnall, Menomonee Falls, Whitefish Bay, Slinger, South Milwaukee, and Greenfield.