A is the main door to the classroom.
B and C connect the outside to a foyer with the restroom and another set of double doors leading into the classroom.
This is door A. It stays locked. (They all stay locked.) The only time it's propped open like this is between classes when I'm sitting in that chair.
The right-hand door is never used and is covered with paper to prevent people from seeing in.
The left door is not covered, but it is still difficult to see through.
During a lockdown drill, I pull that black out curtain across, and it completely prevents anyone from seeing in.
Students are not allowed to open the door for anyone, even if they are standing right at the door and can see that it's a classmate.
This is door B. Normally, that table is not blocking it. (Fire Code violation.) It's only propped open when we are outside on our "patio" cleaning paint brushes.
This is door C. It doesn't get used much at all. During football season, they let game visitors pass through to use my restrooms.
What would really increase security would be to get some rolling shutters like these.