We have about 260 buses running every day with 3 to a seat. Even high school route buses are full to capacity. The state of Illinois keeps cutting school trasportation funding, so every year its less buses and more kids.
The 3 to a seat always amazes me, particularly with middle/high school kids. One solution to this is the 42" wide seats that are available with the Lion, I sat with another adult on that and was impressed at the difference just 3 inches makes. However, that is something that I don't think we will see with any of the "Big 3" bus builders unless more operators require 102" wide school buses.
Kids these days just aren't the same size they were back in the 50s/60s when the seat rules were created!