The transition to primary school means the end of preschool and the beginning of the school period in a child's life. During preschool education, the child develops the skills necessary for continuing education and acquiring academic skills. It is important that the child reaches a certain developmental level by the end of preschool education, which will promise the smooth acquisition of new knowledge and skills in primary school education, both academically, as well as socially and adaptively. Adequate developmental level, i.e., the child's readiness for enrollment in the first grade of primary school, is determined by the expert committee for determining the child's psychophysical condition. According to the information obtained from the assessment of the child and the discussion with the parents, the expert committee approves enrollment in the first grade, proposes a postponement of enrollment or suggests an appropriate form of education for the child. Sometimes the proposal to delay enrollment is put before the parents unexpectedly, since they have not noticed a significant deviation in the child’s behavior compared to his peers. Milestones of development are very useful for this; scales for informal assessment that the professional staff of the pre-school educational institution can apply to determine in which areas the child needs to be encouraged. The regular use of development scales directs the work of educators and professional associates and helps predict the outcome of the transition period. The aim of this research was to compare the results of the assessment of preschool children in some areas with the outcome of the process of determining the child's psychophysical condition for the purpose of enrollment in the first grade of elementary school. The sample included fifteen preschool children without disabilities from a kindergarten in Zagreb. The research was conducted using a questionnaire from the Assessment, Evaluation and Programming System® [AEPS®]. The results obtained on the AEPS® scale were compared with the decision of the expert commission for determining the child's psychophysical condition on enrolling the child in the first grade of primary school, and it was determined that all children who achieved results in all areas above 85% on the AEPS scale were enrolled in the first grade of primary school, which confirmed the research hypothesis. A comparison of the assessment using the AEPS® scale and the decision of the expert committee gives us valuable information about the suitability of this measuring instrument for the Croatian population.