How to Go Behind the Teacher's Desk in Big Nate

Head right from the area you start in after landing on Big Nate Island. When you arrive at the schoolhouse, enter it. If you are unsure which building is the schoolhouse, look for a building that has the word "knowledge" written above the door.

Go up the stairs to the right and enter the science lab, which is slightly to the left of the stairs. One required comic book piece is on the left side of the lab above the skeleton. Another is located outside the lab, to the right of the staircase. You should already have most or all of the other pieces.

Click on the chemistry set to the right of the boy wearing a green shirt -- the only person standing in the lab besides yourself and Big Nate.

Fill the beaker half with blue chemicals and half with yellow chemicals, and the mixture will be green. Then turn the heat to four. The mixture turns into a stinkbomb, which you need to move the teacher from her desk.

Continue to play through the game, until you are thrown in detention for chewing gum in school.

Set off your stink bomb, to remove the teacher from her desk and gain access to the secret room behind the filing cabinet.