Talk to Elisa and Antoine, then walk to the library to find out it is locked. Walk to the girls' dormitory hallway and talk to the Foreman to find out you are not locked in. Return to the Chat Room and talk to Antoine, asking for his sandwich. Go to the Lecture Room and talk to the Principal to get the key. Retrieve the book from the computer table and bring it to Antoine, then accept the cheese sandwich. Bring the cheese sandwich to the Foreman,  then walk into Elisa's room and get the stationary, which is on the far back table. Return to the Chat Room and give Elisa the stationary.