noun
nursery school child; preschooler (in daycare)
Refers specifically to a child enrolled in a 保育園 (nursery school/daycare), typically before elementary school age.
保育園児たちが公園で遊んでいる。
The nursery school children are playing in the park.
うちの子は来年から保育
My child will become a nursery school kid from next year.