In high school I missed ~15 days each of the first 3 years, ~20 my senior year. They always sent truancy warning letters at 10 days but since I was near the top of my class they never made it a problem
I was skipped about once a week my last semester, my schedule sucked and I was just over it...
In college, last semester I started to skip Chemistry near the end because I was so lost and my professor was a useless asshole. This semester I only skipped a few lectures because I had papers due and my classes were a lot more lecture based.