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Our district is still using omnibus grades correlating to an overall
percentage score (A = 100-90, B = 80-89…). Our middle school has been
championing standards-based grading for several years, but we recently
found our staff divided by a conversion practice that has been adopted
by some but vilified by others. The conversion practice, dubbed “Base
50 scaling,” entails weighting test items according to complexity
level and adding “earned points” equal to a maximum 50 points to a
“base” of 50 points for a total possible of 100 points. In other
words, up to 50 points are earned by correctly answering test items,
and these earned points are added to the base (automatic) 50 points.
Supporters say this achieves the SBG goal of creating an equal
interval system. Detractors say this magnifies the inaccuracies of
percentage grading by inflating scores at the lower end of the
spectrum. Since this practice is being inconsistently applied while
we debate the issue, I fear we are jeopardizing our goal of district-
wide SBG adoption by reporting such inconsistent grades to students
and parents. What are your thoughts (or suggestions) on this
conversion method?

Kim Barker


I think it is way too complex and, as suggested, that it magnifies the inaccuracies of the
percentage system." A far better approach is to score everything using levels and then use
a logic rule to convert to letter grades, e.g., Mostly 4's, nothing below a 3 = A,. For tests
you would have to determine the cut scores for the levels, e.g, easy out of 20 - 18 -4, 16
3, 14 - 2, Below 14= 1; difficult concepts, skills, test - 14 - 4, 10- 3, 8 -2, Below 8 = 1.