The garbage can
On page 3, readers can see a student holding a garbage can over their head, while their classmates throw paper airplanes and spitballs. This imagery underscores the students' immaturity and reinforces why Miss Nelson decides to leave her classroom and become Mrs. Swamp. The students in her class are clearly out of control, and she needs to rein them in.
The contrasting imagery of Miss Nelson's pink sweater and the classes' dark clothes
The contrasting imagery of Miss Nelson's pink sweater and the classes' dark clothes reflects their overall personalities and actions. On one hand, Miss Nelson is a kind woman who wants the best for her class. On the other, the students in her class (who wear dark colors) are focused on doing malevolent and disruptive things, causing a lot of frustration.
The contrasting imagery of Mrs. Swamp and Miss Nelson
The contrasting imagery of Mrs. Swamp and Miss Nelson reflects the attitudes the class holds about each teacher. Mrs. Swamp, who is clad in nearly all-black with long nails and a big nose, brings order to Miss Nelson's classroom. To do, she must be abrasive and hold the class to account for their misbehavior. Miss Nelson, on the other hand, is dressed very brightly and appears to be very kind. This contrasting imagery explains why the class doesn't like Mrs. Swamp and why Miss Nelson decides to leave and become Mrs. Swamp.