First of all, let us say that improvement in the areas of memory and concentration can be expected from every single child.
Let us keep in mind that all children have differences in capabilities and therefore the results will not be identical. However, in an overall sense, every single student displays improvement in his own way. In some cases, the parents desire results in a single aspect, making them blind to see progress their children had made in other areas. In situations like this, we as professionals, guide the parents so they can comprehend the developing process. Eventually, the parents will see that everything will fall in place, and in the end will see their children bloom.