In Indiana track and cross country start in 4th grade. That was really a surprise to me when I moved here but I guess it is good. The program at my kid's school wasn't very good but at least they had a team. A teacher that had no interest in running whatsoever was the coach. He coached for the extra money only and put no effort into his job. But still, the kids got some early conditioning and introduction to racing.
The XC races are short of course, 1 mile if I remember correctly. There was only 3 or 4 races in the season with the other elementary schools in the area.
A coach that has an interest in the goods doing well is probably the biggest factor in a succesful program. At that young of an age, training is minimum but interest and fun is a main concern.