Well despite that Azumanga Daioh is about a story of friends in their attempt to make their daily life at school fun with their annoying teacher it has been one of the best school comedies produced.
Though there is no story or plot behind the anime, the randomness that it creates along with it's whimsical comedy leaves a feeling of wanting to watch more!
If you're into comedies and high school girls, I highly suggest that you watch this anime.