I hate act to like PEZ, but, "school vs. shoal" needs addressed.
A school of fish, is a tight mesh of fish, that move simultaneously as one unit. A giant ball of herring trying to avoid predators, for example. Outside of the occasional Golden Pilot Jack, that makes it way into the trade, you won't find a fish for sale that technically "schools." All aquarium fish that have been mentioned, and will be mentioned, "shoal;" a loose collection of similar fish, not necessarily same species, whose actions are similar, but usually independent. A shoal of anthias, for example.
Firefish aren't recommended as a shoal fish. In the wild, they only form pairs. Three or more can cause problems. Perhaps in a large enough tank you could try two pairs, but more often then not, it doesn't work out.
Cardinals or Anthias are good choices, though I definitely wouldn't call Anthias easy. They have quite high dietary needs (3x a day feedings), and are quiet prone to diseases, mainly internal parasites. The rigors of the current retail system, collector-to-wholesaler-to-distributors-to-retail outlet, takes it's toll on Anthias as they are not feed properly during that time period (at best, 5 days). If you decide for Anthias, look for healthy specimens. The body should not have a 'pinched' look behind the eyes, sunken stomach, etc.
