> There should have been and were lockdowns early in the pandemic. Once vaccines were available teachers should be ready to teach, just like every other worker that interfaces with people.

Isn't this largely what happened in the US? Vaccines started to become available in early 2021, but generally only to health care workers and the most vulnerable. It wasn't until around April that they were available to most adults, with the mRNA being by far the most available. If you jumped in as soon as they opened up general availability it would be early to mid May before you were considered fully vaccinated (Two weeks after second shot).

That's near the end of the 2020-2021 school year.

And remember, that's for people who got vaccinated soon after general availability. In a lot of areas demand was outstripping supply, so it could take a couple weeks or more to actually get an appointment.

By the start of the 2021-2022 school year, everyone that wanted to get vaccinated could easily get it for no cost and very little effort, so in-person school has been very widely offered.