as "lateral line" said, almost any fish will school. they need plenty of area, some of those fish are:
>tetras (any kind)
>barbs (almost any, usually the smaller ones)
>cichilds (angelfish, discus, africans,hatchetfish, etc.)
>guppies (about the only schooling livebearer i can think of lol)
>and a wide variety of marine fish ( which i won't go into)
>catfish (a few species will, but i'm not sure of the exact ones, i'm not a catfish person)
so as you can see, pretty much any fish you would want to keep.