This document is an English-language abstract (approximately 1,500 words) of a Bulgarian study of six-year-old schoolchildren. Data gathered in a number of countries where children are enrolled at school at the age of six is a sound basis for analytical study; in nations where the enrollment age is seven, such as Bulgaria and the USSR, children's capabilities are often underestimated. Because of trends in the more rapid development of children due to better nutrition, technology, communications, and other factors, the traditional periodicity and stages of public education should be reconsidered. Recent experiments in Bulgaria in starting children in school at the age of six have shown many favorable results. Further experimentation is needed to arrive at the optimum curriculum. Institutions which train elementary school teachers must revise some of their courses to accommodate the younger children. Medical observations covered 190 pupils in experimental classes and 250 pupils in control classes; all the examinations were carried out both at the start and at the end of the school year. The experiment started at the beginning of the 1961/62 school year and finished at the end of the 1964/65 school year, covering the whole period of elementary schooling thus generating data concerning the long term effects of starting school at six. (Author/GDB)