"My child has good grades in Estonian. There shouldn't be any problems with the exam."
Many parents think this way. And they are very surprised when a mock exam shows a completely different result.
This happens much more often than it seems.
It's not that the child is a bad student. It's just that school grades and the B1 exam test slightly different things.
Quick Answer
Even if a child does well in school, they may lack speaking practice, confidence, or experience with the specific exam format. All of this can be developed beforehand.