I am two-minded about music assessments at times. I see the value in them as checkpoints in a child's learning. However it does become restrictive and almost detrimental when:
(a) parents/teachers peg a child's musical abilities and potential to the grades and results attained;
(b) parents/teachers/child impose a timeframe as to when a certain grade should be attained;
And in a most bizarre fashion, when...
(c) both parents/child do not invest time in quality practice but expect good results by just attending weekly classes.
Music exams can be a time to focus on certain skills (out of many) such as sight reading, aural awareness and repertoire which builds techniques in a progressive manner. It could possibly be an event where the child gathers comments and advice from another specialist apart from his/her teacher...
Whatever the case, exams should remain what it is meant to be - a tool to gather feedback in the process of consolidating skills and knowledge in his/her lifelong journey in music, and definitely not an end goal to a child's music learning journey.