Objectives: Our research aimed to examine children's sleeping habits from preschool to the end of elementary school age. Developing proper sleeping habits in childhood is essential, as it is decisive for the rest of our lives.

Methods: A total of 339 children (160 males and 179 females) took part in the research, of which 145 were preschool-age children (3-7 years old), 72 lower-grade elementary school children (6-11 years old), and 122 upper-grade elementary school children (12-16 years old). The questionnaire was completed in a paper form (elementary school students) and online (kindergarten children).

Results: The research results show that most of the children spend enough time sleeping following the recommendations. In case of the kindergarten children, the younger ones also sleep in the afternoon on weekends (average of 3.66 years, 28.3%), and the older ones do not sleep in the afternoon either in kindergarten during the week or at home at the weekend (average of 5.22 years, 46.2%). The use of blue light typically increases with age; 39% of the preschoolers, 61% of the 6-11-year-olds, and 67% of the 12-16-year-olds use it before falling asleep. Sleep aids and rituals are used by 87.6% of the preschoolers, 67.4% of the 6-11-year-olds, and 34.4% of the 12-16-year-olds, because significantly more preschoolers find it more difficult to fall asleep than older children. At night, 40% of the preschoolers wake up at least once (due to biological needs - 46.3%), 32% of the 6-11-year-olds wake up at night (due to nightmares - 42.3%), and 41% of the 12-16-year-olds also wake up all night (due to biological needs - 31.9%, and due to noise - 29.8%).

Conclusion: Although the children get enough sleep, significantly more upper-grade school children feel tired in the morning. It is essential to help sleep and eliminate factors that prevent falling asleep to create a healthy circadian rhythm in the life of children.