The research focuses on the diagnostics and stimulation of socially disadvantaged children of a preschool age, which is a crucial component of inclusive education. The aim of the research was to experimentally verify through input and output orientation diagnostics the effectiveness of the stimulation program for 5 to 6 year old socially disadvantaged children in kindergartens. The results of the input and output orientation screening of 5 to 6 year old children from the experimental and control groups were analysed. Furthermore, the effectiveness of the stimulation program intended for the training of areas of deficits of partial functions and symptoms in the experimental group was verified, and conclusions and recommendations for pedagogical theory and practice in the area of inclusive approaches at the preprimary stage of the school system were formulated. The research demonstrated that the experimental group of children achieved statistically significantly better results in the post-test, focused on the area of symptoms measured by the t-test, than the control group. It was also confirmed that both groups of socially disadvantaged children (control and experimental) achieved statistically significantly better results in the post-test, focused on the area of deficits of partial functions, than in the pre-test.