I drove a school bus(gas) , back when you kept a bus at home and was a student driver. My route was about 25miles
So
50miles a day@ 7mpg=7.14 gallons per day x 5 days=35.7 gallons per week.
36 gallons x 36 weeks of school =1296 gallons of gas x say $4.00 per gallon here= $5180 per year
$5180 x 5 years = $25,920
Much less than $100,000 battery replacement.
Plus the gas bus is good for 10-15 years with no engine replacement.
EV bus will probably need batteries every 5-7 years
I'm sure there are short or longer bus routes, and more expensive fuel in some places, and even year round school.
It might even be worth while to have an ev bus if they go to school year round.