The most popular schooling fish are probably chromis, cardinal fish, and anthias. For a 29 gallon tank, you could keep a pair of cardinals (they tend to stick together like a school), but it's really not large enough for a school of anything.
Several types of anthias could be kept in a 90 gallon tank, and I have a small school of chromis in my 90. Chromis are pretty and cheap. Anthias can be difficult to keep, and are more expensive. But so beautiful.