Here we have a graph of both the Algebra I and Algebra II Common Core Regents exams in New York State for June 2016.
Although Algebra II is awarded an average of 1.39 more points than Algebra I gets, with a maximum 4 points more, and a minimum of 0. Algebra II never lags behind Algebra I.
(Please note, I am not commenting on the relative difficulty of the tests.)
What interests me is the "closeness" of the two graphs. Both give a fast track to a scaled score of 65 (minimum passing grade) and then slow down as they approach the top end.
Easy to pass, hard to ace. It certainly appears to narrow the achievement gap.