Does anyone have a good sci-fi anime recommendation?

Okay, so I need something new to watch. I really liked The Melancholy of Haruhi Suzumiya. Deathnote bored me from what I watched. I got about five episodes into it hoping it would grow on me, before I finally gave up. And although it isn't a sci-fi I loved Ouran High School Host Club.

I particularly enjoy the school settings, as you've probably guessed. So if anyone has anything similar to MHS because of the sci-fi or OHSHC with the comedy I'd really appreciate it!