I remember showing up for tenth grade, looking at the list of assigned classrooms in the first day of the school year. Instead of the usual the digit number, it said “C1”. My classmates showed up, and we’re just as confused as I was.
The C turned out to be short for “container”, which we found in a corner of the school grounds.
That said, being able to quickly go outside in every break was pretty neat. And the school actually did get a second building only a few years later.