When organizing baseball practice, it is suggested that the section of practice we call, Individual, last about 20 minutes and include at least 2 different drills.  We’ve found with college players that concentration diminishes after 6-8 minutes.  With younger players you might want to do three different drills.  A little competition with this one from the iBook, Practice Baseball to Win, will add some spice.  For more about Practice Baseball to Win go to: practicebaseballtowin.com