The aim of the study was to assess schoolchildren's knowledge on sun exposure, the peculiarities of behavior in the sun, and the possibility of altering these indicators via education program. The study of the efficiency of the self-designed educational program "Let's know the sun better" included 213 fifth grade pupils (113 boys and 100 girls) from Kaunas city schools; the pupils were differentiated into two groups: the experimental (n=106) and the control (n=107) groups. The method employed was anonymous questionnaire-based inquiry. The data of the inquiry applied before the application of the educational programs showed that schoolchildren's behavior in the sun is careless: 40.4% of the studied schoolchildren experienced severe sunburns; 54.0% of children spend three and more hours on the beaches, most frequently between 11 am and 3 pm. Not all schoolchildren use sun protection measures. Most frequently they only have bathing suits (70.0%), baseball caps (56.8%), and sunglasses (57.7%). Out of the studied schoolchildren 18.8% use sunscreen, but only 7.3% of them know how to use it properly. The second inquiry was performed after the schoolchildren were able to apply the recommendations of the educational program "Let's know the sun better" in practice during the summer. The data of this inquiry showed that the knowledge, attitudes, and the peculiarities of behavior in the sun in the experimental group were better compared to the control group. Significantly more schoolchildren in the experimental group (44.1%), compared to the control group (8.5%), used sunscreens properly (p<0.05) and knew which sunscreen is the most suitable (respectively, 42.3% and 20.6%; p<0.05); in addition to that, the children in the experimental group more frequently wore long-sleeved shirts on the beaches (21.0% and 7.5%, respectively; p<0.05), wide-brimmed sunbonnets (37.1% and 10.4%; p<0.05), and sunglasses (61.9% and 44.3%; p<0.05). The findings of the study proved both the necessity and the efficiency of the prepared educational program.