You can just walk out.
The object is to get the teacher out, so you can enter the secret room. However, if you end up in detention without the stink bomb or the blueprint, just exit the door.
Recovering the comic strips to get the gum also gives you Nate's locker combination. Use it to get the blueprint for the secret room. Go to the science room and make a stink bomb (mix blue and yellow chemicals and heat them). Now when you chew the gum and get detention, you can use the stink bomb there to get rid of Mrs. Hargrove, and enter the secret room behind the file cabinet. The light is at the bottom and the Bell Clapper is hanging from the ceiling.
(see related question)
in the detention room.
drop the stink bomb
chew it in school and go to detention
To the detention room but you have to get gum to chew on but not from the poptropica store
in the detention room
Chew the bubble gum
It it in the secret passage in the detention room on Big Nate Island.
you have to get detention with the bubblegum and then use the stink bomb in detention.
it is in the drawers on the right bottom two drawers
in the detention room on big nate island
Go into the school, by the detention room, then chew it! That's how you get into the detention room! Hope this helped!
In the file cabinet, in detention, in the school.