School has been in session for a few weeks, and already, the number of positive COVID-19 cases are telling a story of mask effectiveness and spread of the virus. Continuing Coverage: Coronavirus in WisconsinHere's how the schools match up.In Germantown, where masks are optional, cases are spiking right now at 111.In Greenfield, the student body is a similar size, but masks are required, they have 12 active student cases.Masks are optional in Oak Creek-Franklin School District, another hot zone, with 79 students COVID-19 positive.Compare that to Wauwatosa, where masks are required, there are 26 student cases."We would absolutely expect to see more cases in these school districts that have made masks optional," said Dr. Jeff Pothof, of UW Health.Doctors said the numbers don't lie, and it's why they have pushed for mandatory masks since before the school year began.Milwaukee Public Schools has nearly 80,000 students and 604 current COVID-19 cases. The district requires masks.Masks are optional for Waukesha schools. They have 192 active cases.MPS is more than five times larger, yet percentage wise, it has fewer cases than Waukesha.It's why some schools are now reconsidering current mask policies."Masking is something that needs to be done by everyone to be effective," Pothof said. "If you have a situation where one kid is masked and one kid is not masked, if that unmasked kid has COVID, that masked kid is very likely to get COVID.""I mean, scientifically, if you're not wearing a mask, you're exposing yourself to more respiratory droplets, and that's how it's carried. No, it doesn't surprise me at all. I'm glad they wear masks here," MPS parent Peggy Moore said.WISN 12 contacted Germantown and Waukesha schools to ask them about their latest data, but they have not responded to the requests.Sign up for coronavirus email alerts from WISNGet breaking news alerts with the WISN 12 app.Follow us: Facebook | Twitter | Instagram | YouTube