The three most obvious responses to the successful accomplishment of a task are: that it is a clever, a good, or a right thing that has been done.
But just imagine what the children are learning: that merely to accomplish a basic task that all young people should be able to carry out is an unusual success — that it is intellectually admirable, morally admirable, or ethically correct above all.
I think it's all right to do some positive reinforcement. 'Keep going', or 'yes, this is what you should do' is a suitable response. But the really good responses are all too often used so much that they lose power. In the end, these parents have to call normal acts 'good' and above-average acts 'excellent' just to keep the reward system going.
Daft, I say. At least compensate by heavily punishing the negative acts, or something. After all, inflation should work both ways.