The objective of the study is to convince educational researchers of the necessity for "standard mastery curves" for the graphical representation of scores on summative tests for a group of students. Attention is drawn to the study of theoretical and empirical skew curves in education and biology. Use of standard mastery curves and study of skew curves in statistics and biology is in consequence with the basic idea of mastery learning. It seems to fill the gap between felt pressure to reach mastery and the relative measurement devices available. (Author)