There is an electrical "breaker box" down below the ladder. A blue hand will appear when you roll over it.
The entrance to the hidden room is in the second drawer of the filing cabinet. You need the blueprint from Nate's locker to access the room.
Find the crowbar-like thingie.
by the green cabnit and what is useful in the secret room is the bell clapper
The missing bell clapper is hanging from the ceiling.
As you go into the floor behind the filing cabinet in the detention room, the light switch is right at the bottom of the ladder, on the floor.
You have to find the switch, which is down near your feet, and push it.
You have to find the switch, which is down near your feet, and push it.
Well go into the school and start chewing gum, the princpal will get mad and take you to detention, then use the smelly stuff to get her out of the classroom and then click on filing cabinet and you find a hidden room with the clapper inside:)
It is in the secret store room behind the filing cabinet in the detention room on Big Nate Island. You need the blue prints from Nate's locker in order to access the secret room.
The hidden room contains the bell clapper for the school bell in the tower. Get the clapper (hanging from the ceiling), and when you can scare away the seagull from the tower, you can fix the bell. (see related question)
When You Go Into The Secret Detention Room And you jump down the Light switch is on the wall.
The missing bell clapper on big nate island is in the secret room under the detention room turn on the light and go to your right and jump on the tool table and above you is the missing bell clapper just jump at it and it will go into your items.