Posted by on 29 August 2012 12:37 PM

Value-added is a measure of progress over a given period of time.  ALIS and CEM IBE compare results of post-16 examinations to performance in examinations immediately prior to the sixth-form or to scores from tests taken at the beginning of a student's sixth-form life.  The value-added measure, then, is the difference between a student's actual grade (appropriately scaled) minus their prediction for the subject from either (I)GCSE or the Test.

Measuring different things: prior achievement and developed ability. comparison of the two value-added measures adds a third aspect.  Prior performance may not have been a good reflection of a student's ability.