Say you want to become a private investigator. You go to a detective training institute ... Can you call classmate someone who attend the same courses as you do?
I'm hesitant to do this because according to Oxford Dictionary:
a fellow member of a class at school, college, or university.
It doesn't say institute.
But maybe this doesn't matter as long as there is a classroom?
If you can't call such person "classmate," what should you call them?