I just had to write 450 words about the plot of The Secret Life of Pets for School.

 You had to write about a story with a traditional rising and falling action plot structure 

Pets  was the only story I know simplistic enough to work,

 

Here's the ridiculously clinical plot structure of Pets;

 

Secret Life of Pets

 

Exposition: Duke enters Max's home, upending Max's relationship with his owner, and the two conflict in their relationship. Max plots to have Duke kicked out of the house, when his plan fails he and Duke are captured by animal control after being assaulted by a cats. Him and Duke are freed in a coincidental Flushed Pets operation to free a member, the pair agree with the groups leader Snowball to join the underground organization as compensation.

Rising Action: After being found to be domestication sympathizers, Duke and Max are attempted to be ritually sacrificed by the Flushed Pets; the dogs then accidentally kill a senior member, escape and flee to Brooklyn. Duke is picked up by animal control in front of his dead former owner's house. Max pursues the Animal Control truck, several high-ranked member of Flushed Pets are also taken by Animal Control in an attempt to capture Max. 

Climax: Snowball and Max realize they must work together to stop the truck and free their friends. They hijack a bus and crash it to stop the truck on the Brooklyn bridge. Humans flee the scene and the truck careens off the side of the bridge, only being stopped by unstable repair scaffolding. The main apparatus of Flushed Pets arrives accusing Max of attempting to kidnap and eat Snowball, who has been knocked unconscious by the crash. The mass of animals have surrounded Max, when Max's friends from the apartment building arrive; a brawl ensues and the area is eventually cleared of Flushed Pets. Max crawls down to where the Truck is, the members of Flushed have already freed themselves, but Duke is still trapped in the cages of the Animal Control Truck. Max tries to get the keys from the dashboard, but in the process turns on the windshield wipers switch, sending the truck careening into the east river. All hope seems lost when the Keys are pulled out by the current, and Duke is trapped as air slowly leaves the sinking truck. But Snowball, seeing the keys float to the surface of the water, jumps from the Brooklyn bridge to deliver the keys to Max in the sinking Truck. 

Falling Action: Duke is freed and him and Max swim to the surface. The animals rejoice as all is forgotten between the Flushed Pets and Duke and Max. 

Resolution: Duke and Max find a new close relationship forged out of their experiences. Max also begins romantic relationship with a neighbor, and Snowball is picked up on the street by a young girl, and leaves Flushed Pets.