RE: Schools. In my opinion (and there are reasonably good, but not great, data to back this up) schools can be open and be safe, even with circulating virus. Before there were vaccines, schools were open and in person in many places in the world, some of which had higher rates of community spread than we do now here in Oregon/Multnomah county. These schools had strict mask mandates in schools, upped ventilation and had regular random testing. The thing that I feel is missing (and I have been preaching this for a while) is wide access to low cost or free testing, even at home testing. More of an issue when these schools were open seemed to be transmission outside of the schools, such as playdates, birthday parties, family gatherings, etc. (Schools are easier to control, unless you have politics getting in the way. . . .). Personally, however, I would be concerned about teachers being vaccinated if my kids were under 12 (both are older and have been vaccinated). That being said, bring on the vaccines for kids ASAP!
RE: Vaccine Approval. I don't know why it is taking the FDA and CDC so long to approve/recommend vaccines for 6-12 year olds. Personally I am surprised that it is taking so long, but I am not a regulatory expert. Probably because they want as much data on safety as possible, given the rare cases of endocarditis and unusual clotting with some vaccines. That being said, as far as I know, there is nowhere in the world that any COVID-19 vaccine is approved for 6-12 year olds. I think that the USA was one of the first to approve vaccines for 13-16 year olds.
RE: Infections, disease and vaccines: One thing that I always try to emphasize, but often seems to be lost, is that infection is not the same thing as disease. I admit that I was skeptical when the WHO named the virus SARS-CoV-2 and the disease caused by the virus COVID-19, but now I think that it helps to understand that the vaccines were designed and tested and approved for protection against the disease (COVID-19) not against infection by SARS-CoV-2 (this is one of many reasons that I really dislike the term "breakthrough infection", but that probably needs to be another blog post). Unfortunately most people talk about the COVID-virus, which is not correct. One analogy that I like is that the vaccine is like a fire extinguisher, it does not stop a fire from starting (infection), but it can stop a fire once it starts (disease).
RE: Delta variant. As far as the Delta variant is concerned, it is still SARS-CoV-2, and a Coronavirus, so all of the non-pharmaceutical interventions work just as well with this variant as all others, i.e. masks, distancing and ventilation. From epidemiological studies and a few case studies, it appears that Delta can spread from person to person sooner after infection, and MAY be somewhat resistant to pre-existing immunity, either from vaccination or previous infection. But it is not clear at all what causes this and how much has to do with people "letting down their guard". The big outbreaks in India were after major large group events, and in the USA after July 4th, and when people basically seem to have thrown away all of their masks (I am less sure about the spike in the UK, maybe the European Soccer championships). Still, just like for all of the other variants of SARS-CoV-2, vaccinated people do much better than non-vaccinated people when infected with the Delta variant of SARS-CoV-2. On average, the vast majority of people with severe COVID - from whatever variant - are non-vaccinated.