This site can give you a list of resources that will tell you all you need to know from elementary to college age level. There are always advantages and disadvantages to any strategy. The University of Western Australia has put out a list of advantages and disadvantages of small group learning. More resources can be found about small group teaching at this site by the University of Waterloo. Waterloo also has a list of resources to be found.
Experiments are a great part of finding out if different strategies really work.
Find out if small group discussion is a good strategy to use in the classroom. This is a small group interaction experiment that was done in a second grade mathematics classroom. Quotes and comments from the paper written about the experiment are given at this site. This site gives you information about small group discussions, when to use it, when it can be useful in the classroom, and how to use it. Community Share is a school book club program that was designed to use whole group and small group discussions in them.