Drill is repetitive exercise of a skill or technique. The School Drill is a student demonstration of skill level achieved in training. One problem is fatigue and another is the onset of boredom. Learning stops when the brain in no longer engaged due to either issue. Whether you have 5 students or 30, a few need continued repetition beyond what the remainder need. If the entire group or relay is held back with the slower achieving students, fatigue and boredom are issues. If the more advanced are moved on while the slower group works to keep up, frustration and desperation set in.