I was notorious for being absent from school. I actually did very well academically, and because of this, teachers did not call me out on missing a lot of class. They kind of looked the other way, as I still did my work & did it well, aced the tests, and was well-behaved when I did attend.
In middle school especially (ages 11-14), I sometimes faked illness to stay home, but I was also legitimately prone to bad migraines as a teenager. My parents were the kind who'd sign anything I stuck in front of them, so my absences were always excused with parental notes. In HS I did not miss quite as much school, especially in the last two years as I was ahead on credits & left at noon (making it though half a day was less daunting).
The reason I stayed home from school a lot was:
- The social pressure & energy-drain of interaction. I was very shy, felt awkward & out of place, and I had few friends. Sometimes I just needed to hide away from it all. I'd prefer to stay home with books & music & daydreams. The social part of school was what I hated; I've always liked academics & learning & done well in it.
- I was bored & arrogant. I figured if I could get straight As just going to school 3 out of 5 days a week, then why should I go everyday? Since I did not want to interact with people & I already knew the stuff we'd be learning, then I knew I'd just be bored & drained by school, and so I'd stay home. I felt justified in it.
- Lack of structure & laziness. Sometimes I just did not want to get out of bed on time or follow a schedule. I was not good at keeping routine (I'm still not). It was easy for me to just stay home when running late or unprepared for class. I missed the bus a lot too

. I'm very mood-oriented & would allow myself to spontaneously change my plans for the day on a whim. I'd literally be listening to a song & decide I did not want to go to class because I felt like staying home & listening to that song instead.
I didn't miss college classes because it was an entirely different environment with different social & academic expectations. I really liked college & never felt like I wanted an excuse to miss class.