Hello!
In theory, that should work perfectly, but maybe something is wrong because of one of the latest changes made to the game. I'm going to test it, I'll write to you again soon. I'm sorry for the problem caused.
Hello! I've already seen the bug. The place to put the sign is there. But, after the last changes I made to all the maps to make them more visually beautiful, I forgot to make sure that said place could still be seen. I'll fix it as quickly as I could and post a new update. If you read this before said new update is available, you can continue playing your game, just do the following:
In North Yard, walk to the right door of the gym (they are two open doors together, stand directly in front of the right door). Walk two steps to the right and interact with the wall, the sign should be right there, even if you can't see it.
I am very sorry for this inconvenience. Have a nice day!