You will need to be a little bit more specific about which one of the hint notes, as I do not know which one you are referring to. I know what almost all of the hidden notes mean.
Viewing post in Advanced Education with Viktor Strobovski comments
The hint notes that I'm trying to understand are:
- In the Red Room in the Math level (where you find the Key and the Second Arm)
- In the Hallway with the Pizza Room and the Server Maze room (The two you say that the Headteacher doesn't count as "Staff only")
- Beside the door that can teleport you to the Bunker or back to the start of the Language level