The Type-D school bus uses a 387 kWh lithium iron phosphate battery.
Ideally, rezoning and infrastructure changes would reduce the need for school buses. We don't have the time though, so this is a win. Hopefully production can ramp up and governments can create incentives for schools to buy these instead of dead dino powered buses.
To expand on that, couldn't you also have a separate power source to warm up the bus before it was taken out on a cold morning? Something like an engine block heater for an ICE vehicle.