Perception and memory were tested twice, in the I-st and in the 10-th grade, in the same group of pupils who started studying at school either when 6 or 7 years old. Although at the start they lagged behind by their mnemic and, especially, psychophysiological indices, by the time of graduation the "six-year-olds" are practically at the same level with the "seven-year-olds'; at that they are somatically more sensitive to informational load, and their achievements are markedly higher. Besides that in the tenth-grade pupils who studied from 6 years involuntary memorization is less dependent on the modality of material, and their retrospective quantitative analysis of stimulation is more accurate. Results are discussed in relation to the problem of correlation between the time of the beginning of studying and the sensitive period of memory development when interrelation between conscious and non-conscious mnemic activities of the brain is optimal.