Yeah, my school is really bad and it's better to just study at home. Some of my absence is also for the time after trials but before STUVAC where our school had 'fun' dress up days and that kinda stuff so I just stayed home to study for HSC. For e.g some of my classes you couldn't do work in because everyone is talking/lauging/screaming so I decided to just study on my own once this started happening like every period.
I'm pretty sure if your attendance ends up below 65% in junior years, there may be talks with parents about attendance levels, which should be at least 80%, but even so that is kinda low. I reckon 4 absences in a semester is fine, anything above 98% is good.