Using the method of cross sections, formed trends in the development of representations on the schoolchildren populations are identified. The results of cluster analysis of brightness-clearness of representations of different modalities are provided. It is established that the brightness-clearness of representations of younger schoolchildren is characterized by non-differentiability of the different modalities due to the lack of information from one sensory channel to create a sustainable way of representation. We consider that the result is due to the fact that at this stage of school level information is only stored, cross-checked, and updated. We have found that teenagers' representation is characterized by the differentiations. We believe that on the one hand, the process of allocating the information in the minds of each modality proceeds, on the other hand, the representation of each modality has experienced as separate, isolated, specific condition, that finds the integrity, stability, and relative completeness. The study has found that a feature of high school students' representation is building a clear, consistent hierarchy of brightness-clearness of the representation of different modalities. We have found the maximum similarities in brightness-clearness of representation of visual and audio modalities, which form high students' core structure around which on different degrees brightness-clearness of representations of other modalities are distributed.