I've learned how to drive school buses, and I absolutely agree with your opinion. My first day on the job was my last (well, I drove a bit the next day before refusing to drive in a situation I was not comfortable in); it was just way too stressful thinking about those kids and how any mistake I make could hurt them.
Luckily it's actually pretty hard to hurt kids in a school bus. They are built incredibly heavy and sturdy for exactly this reason -- if you collide with any car other than a loaded semi trailer, the bus will win.
Busses even roll every so often and while the kids are banged up a bit, fatalities are incredibly rare.
But...the irrational part of me still had anxiety about it.
And we were trained about how to evacuate the kids, which we were supposed to do only in two cases: stuck on railroad tracks and fire. And only those two cases because...being on the bus was safer, just as you said.
How does staffing for school bus drivers work? I imagine they have to have a pretty exact number of drivers? They can't really have too many or too few, how close to the exact number do they have to get, or how do they handle underages/overages?
There is almost never an "overage" because there is a driver assigned per route, but they also have a bunch of sub drivers who get paid to show up, wait, and maybe take a route whose driver didn't show up, but if not, they go home after getting paid for an hour of waiting.
That's the gist, but it's a bit more complicated than that; in the school district where I live, bus drivers who were assigned routes actually had two or three per day: one for an elementary school, one for a middle school, and one for a high school. Yes, they are that short-staffed. In fact, all of the buses are advertising paid training because they need drivers that bad.
When I quit on my second day because of the stress about being pushed to get kids to school on time rather than safely, and also feeling like I needed more training to be safe, the head of the transportation department desperately tried to get me to stay.
tl;dr: they have bus drivers on standby who get paid to wait in case routes need to be filled. And they are so understaffed that overages never happen and drivers handle 2 or 3 routes.
Staggering school bus service isn’t that uncommon, I don’t think there are many school districts where their bus drivers only need to drive one route rather than 2 or 3. Not only can the drivers be employed for most of the day, but the bus itself gets more use.
I moved around a lot as a kid so got to participate in many different school districts. Talking to the school bus driver they all talk about their schedules.
Edit: clarified my actual quit story.