Sounds like you found crappies or cisco. I can sometimes tell the difference in certain fish on my graph (a school of rockbass looks very different from a school of perch) but most of the time you are going to be guessing based on where/what you see on the graph.

Probably was a school of cisco but just because you dont catch anything doesnt mean its not a good school of baitfish. We go over so many huge schools of baitfish when at murray but mainly catch fish when there isnt a school on the sonar.