You know, there is no need in general story in this kind of anime. It's all about situational gags, but let's leave 8 points here, just because of girls-only school.
Art: 8
It's pretty nice, with all that chibi-face transformations etc etc. If you are not afraid of that (for example you liked Panty & Stocking with Garterbelt) you'll find art adorable. If you don't, youshouldn't watch this one at all.
Sound:8
Sound in 6 mins episodes? You're joking. What's about SFX they're placed very well, that's why I'm leaving 8 points here.
Character:9
Oh... That... Boobs... I just can't resist, also Aya-chan isn't a shy one, which is quite rare in modern anime. And here is her counterpart in order to shade her. And few other girls. But again, there is not that much time to explain all chars, so for this 6 mins setup I found girls quite catchy. And Aya's boobs again.
Enjoyment:10
That's easy. If you like raw sexual jokes, you'll agree this is 10 points. If you too shy to face it, you won't. I just can say, that I got my jaw nearly dislocated because of laughing.
Overall:9
It's short comedy title. So main parts here art, chars and enjoyment. (8+9+10)/3=9. That's why.
To sum: if you liked PSG for Panty, Hen Zemi or Oruchuban Ebichy forall that silly jokes, you'll like Gokujyo too.
