Previously, GCSE grades ranged from an A* to a U. Under the new system candidates are scored between 9 and 1. The highest grade is 9, which is valued higher than the existing A*.
The purpose of these changes is to allow greater differentiation between the very best students. As a result, fewer students are expected to score a 9 than those scoring an A* under the previous system.
Click here for a BBC article that explains how the new grading system works.