Adults' Inscrutability
One of the major themes in Wayside School Beneath the Cloud of Doom involves the inscrutability of adults. In the novel, adults are portrayed as strange, enigmatic people that the children cannot understand, even if they try very hard. Unlike adults, the children in Wayside School Beneath the Cloud of Doom view themselves as enlightened and normal people that have a tremendous amount of forethought. Ultimately, in their mind, they believe that they are more intelligent and more normal than adults.
Staying Strong Despite Bad Circumstances
Author Louis Sachar said he wrote as a way to deal with issues that nagged him, including the election of Donald Trump and global warming (among many other things). Those bad things are represented by the eponymous Cloud of Doom. Despite that, Sachar (whose book is neither glum nor negative) and the kids in the book have remained upbeat and happy and positive. This is the biggest theme in the book: despite the bad things happening around them, the kids in Sachar's book remain happy and positive.
The Conflict Between External Factors and Human Behavior
An overarching theme in Wayside School Beneath the Cloud of Doom is the conflict between external factors and human behavior. The kids are understandably affected by the cloud of doom that looms over the Wayside School. However, they act out and misbehave; the kids blame their misbehavior on the cloud, eschewing all personal responsibility.
Being Resourceful
A minor theme in Wayside School Beneath the Cloud of Doom is the importance of being resourceful and using limited resources to their fullest, which the kids do in "Breathe" as they don't have access to any musical instruments.
