I have a ten gallon with 4 cherry barbs, 4 zebra danios, 3 baby yoyo loaches and 6 big amano shrimp. The danios spend a lot of time chasing each other around for whatever reason, but they aren't really "schooling."
Maybe it would be wise for me to trade out my barbs for a few more danios to enforce the schooling mentality. Maybe then they'd stop picking on each other as much. There's a definite pecking order, too, but the three smaller ones will gang up on the fat female once in a while. What do you think?