For back to school.... sorry long winded.
Everyone has the two options of either online or in-class for elementary school. While the kids are at lower risk of serious impact (but not zero) IMO the big threat vector is spread to family at home (infected at school, asymptomatic, infect more at school....infect those at home). Most people I know that have higher risk people at home (health or age), or the kids at risk due to issues have opted for the online to protect themselves. Having said that, many people rely on it as daycare and even though in the high health risk category they are sending them anyways.
In the end, the highish online take rate meant that many schools "could" have had much smaller class sizes, instead they collapsed classes together to get back to the regular size, displacing teachers. Those displaced teachers mostly got moved to the online pool. While it would have been nice to take advantage of the smaller sizes due to online take, if they did not collapse classes together there would not be enough online teachers... You have x teachers and y kids...
Teachers in most boards were asked if they wanted to be the online teacher for the same health risk reasons. In the end most boards had a higher online student take than teacher take so they had to repurpose (in some cases force) the now extra (displaced) classroom teachers online. Many that were close to retirement also just opted for that.
Many new teachers (new grads), LTO pool and supply pool have decided to take the next year off to avoid the shitshow, so it is not like they can just increase the number of teachers easily. Even if they could, they would have to fire a bunch in a year or two when it returns to normal.
All this is also why there were delays to the starts for some boards because they needed to rebalance and move teachers around. It is sort of a supply chain management problem. While Ford and team could always do better, this was not as easy a problem to solve as it looks.
The next mess, parents have a small window to change their minds. Kids flipping out wearing masks all day may end up online in a week. That will throw another wrench in the works. After the short window most have to wait until the end of the semester to switch "streams".
And there is always straight up home schooling....