Was walking past the stop on my way to the clinic this afternoon, and there
was a notice on it about "School Buses"

Which basically said "where we are running school buses, don't get on them
if you aren't a child going to school"

and I thought:

There are no school bus routes around here.

And then I saw buses going down the road with a sign in the front saying
"Not School Bus"

So it seems that they are designating some services on ordinary routes as
special school buses and are using this signage to tell you which are which

Haven't been out at the right time of day to gauge the frequency of these
designated buses yet