I prefer the counsel of the American Pediatric Association on this issue, over that of teachers.
U.S. Pediatricians Call For In-Person School This Fall
Following their guidelines and recommendations, you are looking at no more than 15 students in a typical classroom. Most public school class sizes are in the upper 30's to 40's. You also need time to disinfect touch surfaces in between classes and make accommodations for students who need it on campus. So students will be going back to school, but it's not going to be for a full day and it's in many cases it won't be 5 days a week. Schools will be open, but students will be going half day and won't be on campus every day.
I work at a private school and here is what we are doing (14-18 year olds):
Monday/Tuesday - Students either come from 8:30-11:30 or 12:15-3:15. Classes are split into morning and afternoon blocks of 50 minutes each, maximum of 15 students in each. Even classes on Monday, Odd on Tuesday. Non-academics like Athletics and Performing Arts are either before school or after school.
Wednesday - Online Hybrid classes meet for students who want to take advanced courses in a more or less online environment. Students can come on campus for office hours with instructors. The rest of the time is prep and collaboration for faculty.
Thursday/Friday - Same as Monday/Tuesday
Students are required to wear masks and each one is temp scanned and evaluated before they are allowed on campus. Once they are in class they may remove masks as they will be 6 feet apart. Campus will have one-way paths to keep student interactions at a minimum. Students cannot loiter during passing periods. Classrooms will be disinfected between each section, with focus on high touch areas. HVAC will be ran with doors open to increase airflow and remove particles. Students will be in class roughly 15 hours per week, unless their sport is active and they have extra practice time.
This is the only way that students could all be fit into classrooms while maintaining distance and a somewhat safe environment. There was concern after distance learning completed that our enrollment would be impacted and we might be forced to trim faculty, but after releasing this schedule applications are through the roof. We are turning students away as we are at capacity. Most public schools are opening but with even less class time, so we are in demand. It tells you how desperate people are when they will pay close to $20K to get their kid on a campus for a few more hours, longer if they are in a sport (which they also have fees for).
We aren't unionized, so everyone worked closely together to make sure we came up with the best possible plan. Public schools don't have this luxury. They have double our class sizes, less classroom space, and far fewer admin to assist teachers. They only thing they have on us is money, and they tend to squander it.
If anyone thinks a public school teacher is going to be in a class with 40 students, they are sorely mistaken. Their unions will make sure that doesn't happen, and it's not like credentialed teachers grow on trees. I mean, would anyone want to be packed in a space with teenagers who have the common sense of an eggplant?