Turn the lighthouse light to the left using the lobster as a wrench.
To get the lobster:
Catch the old photo blowing near the lighthouse.
Swap it for Scuba gear at the Photo shop.
Dive at Puffin Point to recover Cap'n Salty's lost lobster trap.
Once you scare away the seagull from the bell tower, you can replace the missing clapper and ring the bell.(see related questions)
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)
Once the seagull is gone, you can replace the bell clapper and ring the school bell. To get the clapper: Assemble the comic pieces and get the gum. Use Nate's combination to open his locker and get the blueprint. Mix a stink bomb in the science room. Chew the gum to get detention, use the stink bomb, and go down behind the file cabinet to find the secret room. The clapper is hanging from the ceiling.
The clapper allows you to fix the bell on top of the school, which is guarded by a nasty seagull. Get him to move and you can fix the bell. (see related questions)
Find the bell clapper in the secret room under the detention room, and repair the bell. (see the related question)
They are talking on the playground and will not leave until the school bell rings. Unfortunately, the bell is missing its clapper. Find the clapper, and scare away the seagull atop the school. Then you can ring the bell. (see related questions)
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)
You use the lobster as a wrench to turn the light. The light scares the seagull away and you can restore the clapper to the school bell. (see related questions)
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.
The lobster (believe it or not) is used as "pliers" to turn the knob on the Lighthouse. This will swing the light around to the left, scaring away the seagull from the school's bell tower. Now you can replace the clapper and ring the bell. (see related question)
You have to use the blueprint from Nate's locker, the stink bomb from the Science room, and the gum, to reach the secret room under the detention room. The bell clapper is hanging there, and putting it back lets you ring the bell.
Once the seagull is gone, you must replace the missing bell clapper in the school bell. You can find it hanging from the ceiling in the secret room under the Detention Room. When the repaired bell is rung, the three girls will leave the playground (where you can dig using Spitsy the dog). (see related questions)