School is so depressing because it's so boring and you have to be forced to go to school.
Think of school like a prison or jail where you're forced to stay against your will and cannot leave until your time is up in school.
School is like prison even though you can go home at the end of the day it's like a prison because you're forced to go to school.
Not everyone likes school and being stuck in school, in a building, sitting at a desk and doing school work that you don't enjoy can be so depressing.
I hated school myself and would fake being sick so I could hopefully stay home as I was very depressed in school and I also was bullied and the teachers nor the principal would do anything about.
School eventually gets over with and then you have to go to a job to make a living or run your own business.
I hear some people say they miss school but for me there's no way I miss school and school was not the best years of my life.