When coaching baseball, especially with younger players, it is essential that the fundamentals of fielding ground balls be established before they are exposed to even medium speed fungos.  Time spent to let them gain confidence by using a comfortable pace will be rewarded.  Failure and fear can destroy a young player, so please keep the pace well within their comfort zone.  This drill, form the iBook, Practice Baseball to Win, is one that needs review, even with college players. More about the coaches handbook at Practicebaseballtowin.com