Well. Haters gonna hate.
School Days is not a 'Must-watch' series, but for those familiar with the harem genre it is a worthwhile de-construction. It is very easy to say that the characters are morons; I won't deny that they act like it. It is unlikely such a love triangle would turn out quite so badly in real life. But this is a de-construction. The somewhat shallow, somewhat cliched personalities of the characters are played completely straight until events reach their (il)logical, and messy conclusion.
There's really no point ascribing 'blame' to any of the characters. The big three are affection-starved people at the mercy of strong feelings they don't fully understand, have little of the 'good'/'healthy' kind of confidence in themselves and have no real ability to communicate with each other or anyone else for that matter, and of course no-one else to confide in. Plus, yes, they lack self-restraint. And naturally, there are no therapists. Is it really anyone's fault in particular what happens? I wring my hands. Anyway, do give it a go.
For the record, I'd like to say that I took the series rather hard. I do not like to see characters suffer 'needlessly'. One thing I can say in its favour is the way it really made me appreciate the deeper problems with the harem genre, beyond the gratuitous fan-service and excuse plots. If it wasn't for that, and a sort of morbid fascination with just how bad things could get, I wouldn't have been able to watch things get worse the way they did.
In short, it's the best 'harem' anime I never want to see again.