Preschooler (noun)

A child who is old enough to attend preschool but not yet old enough to attend primary school.

Origin:

Mid 20th century: from pre- + school + -er.

Examples:

1. The teacher works with preschoolers.
2. The preschooler is learning basic skills.
3. The preschoolers are having fun in the playground.
4. She's a preschooler, still in diapers.
5. He's a preschooler, still learning to read.