I don't believe there is a lot of "deep" meaning to Louis Sahar's collection of stories in this, his follow-up to the wildly popular first book in his "Wayside School" series. The goal may simply be to stretch your imagination and get you to think about people and events in new ways.
Here is a short summary of what's going on in this playful text:
As the stories begin, the students are returning to the Wayside School. In the last book, there was a "problem" with cows and the school had to be closed until the problem was solved. It took 243 days to do it, and in the meantime, the students had been dispersed to other schools.
Now they are back, but the weirdness continues! There is still the mystery of the missing but rumored 19th floor; Sammy the rat is back (dead, but still mean). Mrs. Jewels is expecting a baby and this means a dreaded substitute teacher, who turns out to be weirder than anyone could have anticipated.