I think for schooling fish we are pretty limited in saltwater. Anthias and cardinals are all that come to mind. Now, I have five pajama cardinals and they hang out together, but I wouldn't call it schooling. Anthias make beautiful schools. I like the Maldives lyretail personally. A school of a half dozen should give you a good slice of the reef, in a tank that size! One will become male and turn red.
Someone stop me! Please! But... not just yet...
55 Gal Tropical FW
55 Gal Mixed Reef