The STORY in School Days has easily earned it a 10/10 with it's unpredictable ending. Let me just say this now: Do NOT watch School Days if you have not had your fair share of normal, annoying harem animes. When I first watched this anime, I hated it. I couldn't believe I wasted my time on something that ended so freaky. But now that I've seen my fair share of harems (Spring 2011 line up, anyone?) I feel more confident in saying the story was so amazing and so much more realistic.
The ANIMATION was like any other game turned anime. They all look alike to me. Girls are cute, one has big boobs, etc. I honestly don't have anything wonderful to say but it wasn't bad to look at.
The SOUND was fine, but I disliked the OP. And the character seiyuu's also did well and sounded like typical harem girls and an extremely clueless-turned-douchebag main character.
I abhorred the CHARACTERS. All three of the main characters made me want to rip my nails off, but I feel like they were made for you to hate them, especially with an ending like that! I am just happy to see a harem where people react in an absurd way to absurd behaviour.
As you can tell, other than the story, I don't have much to say about this anime. Watch three regular harem back to back in one sitting. Take a break and realize life doesn't work that way and there ARE other animes out there that won't make you want to gouge your eyes out. Then watch School Days. You will be so refreshed and utterly disturbed. Well worth it.