Are schools a major source of transmission for teachers and staff?

Yes. Workplaces with lots of contact always are.

In Nov-Feb, I was losing 40-60 employees a week to infection or quarantine. Mostly people in essential IT support positions

My sons school was open most of the year, but shutdown for a month due to teacher quarantines.

Schools are different than a business setting. Young children have less chance of getting it and less of spreading it. https://www.cdc.gov/coronavirus/2019-ncov/hcp/pediatric-hcp....

You just contradicted the website you linked, I'm confused.

> Hospitalization rates in children are significantly lower than hospitalization rates in adults with COVID-19, suggesting that children may have less severe illness from COVID-19 compared to adults.

Less severe response to it, not "less chance of getting it." And then just two lines later:

> Recent evidence suggests that compared to adults, children likely have similar viral loads in their nasopharynx,7 similar secondary infections rates, and can spread the virus to others

I don't know how you arrived at your opinion here.

The population of humans in schools includes many adults.