I am no expert on perch, especially on the fly rod, though I spent alot of time catching them for fish frys that Mom and Dad had at our camp on the Saint Lawrence. They are definitely schoolers. A) if you are catching and the bite cools off, move. The school you were into is gone. B) If the water looks "perchy", but there is no bite, wait a bit, a school may show up. Though they do school, they seem to travel about within the school in small 4 to 8 fish groups. Weedbeds, and lily pad areas are always good. Escpecially if you can find little gaps to drop into. I think 6 to 15 feet of water is pretty typical. We used to float right into weedbeds, and using bamboo poles drop bait into any gap in the weeds where you can see to the bottom. It was always cool to watch from above as the fish would appear out of the grass, and take the worm/minnow. This website
[url=http://www.execulink.com/~environm/Fishing/perch.html:312a8]Outdoors Fishing Perch[/url:312a8], has this quote regarding small water bodies.

You will find however, that some perch populations, especially in smaller ponds/lakes, may not school up a lot. These fish are the exceptions to the normal and general perch population. These more solitary fish can be caught easily though, once you've found the depth that these fish are in - stay within that same depth during the whole trip out, and cover territory by trying various places within that waterbody.