It's a controversial subject, that's for sure. There's a lot of politics involved and there are people, teachers included, who criticize the education system.
From my own experience, I think you actually have to be kind of lucky with what teachers you have and such. I've had good and bad teachers, but mostly good, thankfully. I also have witnessed cases of "mercy" from the teachers in that students who clearly shouldn't have passed managed to barely pass on the last term, because their grades suddenly rose enough to do so. Apparently, it's a huge mess for the teachers to have one of their students not pass, so in order to save work, they give some extra points to have them pass (grades here are graded from 0 to 20, rounded from one decimal point).