Many people underestimate the importance of a childs ability to simply play. Basic playing fundementals include running, skipping, jumping, throwing, even imagining. These abilities are a necessity for one to grow not only into their own bodies but into well balanced people as well. Fundemental skill developement and assessment is so important because it makes sure that kids are able and getting the excercise they need.
http://www.aahperd.org/naspe/standards/PEPS.cfm is the official site for the National Association of Sports and Physical Education. In this website you will find how and what NASPE feels and thinks about Physical Education classes today. "NASPE believes that physical education is critical to educating the whole child, and that all students in grades K-12 should receive physical education on a daily basis" (Position Statement Summary, NASPE).