A June 8 San Francisco Examiner article discussed measures at the California state and San Francisco local levels aimed at addressing large racial differences in public school discipline rates by generally relaxing the stringent discipline policies in effect in recent decades. The thinking underlying the measures accords with the near universal perception, promoted by the U.S. Departments of Justice and Education and much commentary, that stringent discipline policies tend to cause large racial disparities in discipline rates. Exactly the opposite is the case. Stringent discipline policies tend to yield smaller racial differences in discipline rates than more lenient ones.
Inherent in the shapes of normal distributions of factors associated with experiencing an outcome is a pattern whereby the rarer an outcome the greater tends to be the relative difference in experiencing it and the smaller tends to be the relative difference in avoiding it. The pattern can be readily illustrated with data on employment tests on which some minority groups have lower average scores than whites. Lowering cutoffs has long been regarded as a means of reducing the racial impact of such tests because lowering cutoffs tends to reduce relative differences in pass rates. For example, if pass rates are 80 percent for whites and 63 percent for minorities, the minority pass rate is about 21 percent lower than the white pass rate. If the cutoff is lowered to the point where 95 percent of whites pass, assuming normal test score distributions, the minority pass rate would be about 87 percent. Thus, with the lower cutoff, the minority pass rate would be only 8.4 percent lower than the white rate.
