>> it is alarming, because even though we're all vaccinated, i still have one child that is not. >> reporter: the cdc does recommend unvaccinated students keep wearing masks. that's about 65% of 16- and 17-year-olds, almost 80% of 12- to 15-year-olds, and every student under 12. mask policies will still be set by local jurisdictions, but teachers like jason valenti say they're concerned about how those policies will be monitored. >> i don't know how they're going to maintain that level of understanding of who's got a vaccination, when. >> reporter: over the past two weeks, infections in nine states are up more than 50%. the delta variant now tightening its grip in missouri. springfield's mercy hospital borrowing ventilators to treat more covid patients than any other point in the pandemic. >> we're seeing a lot of more intubations this go around, a lot of healthier people, younger people in their 20s, 30s, 40s that are getting this delta variant or covid a lot quicker. >> reporter: daily vaccinations