30 kids having to sit still 6 hours a day and do nothing more than listen and take notes? That's boring as fuck. Even worse as a lot of the stuff they learn is something they'll literally never even think about once in their life and they'll have to forget again after the test to make room for more useless crap. And every attempt to innovate gets shot down somewhere, so the teachers aren't really willing to adapt either - when I went to school a decade ago we had more than one teacher who used the same transparent sheets on an overhead projector that he made (and copied) decades ago, written on a typewriter.
Smaller class sizes, more teachers, interactive and engaging lessons... that's all stuff that only the private schools (Waldorf and friends) provide and it actually works out even with conventional metrics, but these are expensive and have issues on their own (e.g. the tendency to attract pedos and weirdos, of which there have been a fair share of scandals).
Yes, I'm fed up with the sorry state of our education system.