In Japan, nursery school children go to bed about 30 min later than kindergarteners of the same age. Moreover, nursery school children also reported having several symptoms suggesting more severe daytime malfunctioning. Japanese nursery school children's delayed bedtime was considered to be caused by their long afternoon nap routine, which was obligatorily taken by all students. Japanese elementary schools have no nap routine. This study aimed at investigating how long the delayed sleep pattern of the ex-nursery school children lasts after entering elementary schools. We surveyed elementary school children's sleep-related variables and tested whether there are differences concerning these variables between the children who attended kindergartens (ex-kindergarteners) and children who attended nursery schools (ex-nursery school children) during their preschool period. The total number of survey participants was 981. Ex-nursery school children still showed ‘late bedtime’, ‘sleep insufficiency’, and ‘unwillingness to go to school’, which were their characteristics at the preschool period, even after their obligatory afternoon nap, which was closely associated with those symptoms during their preschool period, was stopped.