You use the bell clapper.
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.
If you have already got the bell clapper, you need to jump to the top of the school and find the bell. Then go to your inventory and click 'Use' on the bell clapper. It should ring and send the children in the playground back.
Once the seagull is chased away, you can use it to repair and ring the bell (which is the only way to get the girls off the playground spot where Spitsy is going to dig). (see related question)
The "clamp" you use to turn the lighthouse light is the LOBSTER. Once you turn the lighthouse light, the seagull will be scared away from the bell tower, and you can fix the school bell and ring it, getting the girls out of the way at the playground.
you get a lobster, then you go to the lighthouse, and use the the lobster by the light
The treasure on Big Nate Island is in the long-lost Time Capsule. (It is actually in the playground, where some girls are at recess. To get it, fix the school bell and ring it. The girls will leave, and you can use Spitsy the dog to dig up the Time Capsule. (Give him a peanut butter treat and he buries it.)
find all the pieces to the big nate comic then you wil get bubble gum chew it in the school then use the stink bomb in thedetention room go to the files there is the bell claper in the cieling then there you are-bryan mendez
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 will first have to have these things: a stink bomb, bubble gum, a bell clanger, and a lobster. You use the lobster as a wrench to unscrew the light in the lighthouse which will scare away the bird the you go up onto the top of the school and put the bell clanger on the bell and it will ring.
use lopster and turn the light on the lighthouse
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 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)