Play the HOP.
You will receive the SAW (Y).
Zoom into the tree; cut the shovel with the SAW (light blue) and take the WOODEN HANDLE (Z).
Go to the Recital Hall.
Zoom into the piano and open the lid with the WOODEN HANDLE (purple); take the FOUNTAIN LEVER (A) and the ALUMINUM PLATE (B).
Go to the Garden.
Zoom into the fountain, put the ALUMINUM PLATE on the crack (C), and fix it with the BLOWTORCH; connect the FOUNTAIN LEVER to the pipe (D), turn the lever, and take the CLASSROOM KEY (E).
Go to the Second Floor.
Zoom into the door; insert the CLASSROOM KEY into the lock (F) and turn the key.
Enter the Classroom.