You need the clapper, which is hidden in a secret room below the Detention Room of the school. You also have to scare away the seagull that keeps you away from the bell. Catch the photo floating near the lighthouse, swap it for diving gear at the photo shop, and recover the lost lobster trap for Cap'n Salty. The lobster can grip the lamp on the lighthouse to turn it, and the light will scare the seagull away.
(see the related solution question)
A person can get the bell clappers in Big Nate Island by talking to the man who runs the comic book store. He will provide you with directions on finding the chest. The chest with the bell clappers is located in the playground on Big Nate Island.
The bell is on top of the school in big nate island
The bell clapper to repair the school bell is hanging near the ceiling. Once the seagull is run off, you can repair the bell with it. (see related question)
Find the bell clapper in the secret room under the detention room, and repair the bell. (see the related question)
You ring the bell
Poptropica
by standing by the bell
The bell on Big Nate Island on poptropica is located on the top school building. To reach it when you have the clapper, you need to get rid of the seagull there. (see related question)
The bell clapper is hanging from the ceiling around the center of the room. You can use it to repair the school bell, but first you have to get rid of the seagull. (see related question)
The only thing in the "secret room" under the detention room is the missing School Bell Clapper, which can repair the bell once you have scared off the seagull.
Up of the school.
It it in the secret passage in the detention room on Big Nate Island.