A preschool, also nursery school, pre-primary school, kindergarten outside the US and UK, is an educational establishment or learning space offering early childhood education to children, usually between the ages of three and five, prior to the commencement of compulsory education at primary school. They may be privately operated or government run, and one option is to subsidize the costs.

Terminology varies by country. In some European countries the term "kindergarten" refers to formal education of children classified as ISCED level 0 – with one or several years of such education being compulsory – before children start primary school at ISCED level 1.

A preschool (also nursery school, pre-primary school, kindergarten outside the US and UK) is an educational establishment or learning space offering early childhood education to children, usually between the ages of three and five, prior to the commencement of compulsory education at primary school. They may be privately operated or government run, and one option is to subsidize the costs.

Terminology varies by country. In some European countries the term "kindergarten" refers to formal education of children classified as ISCED level 0 – with one or several years of such education being compulsory – before children start primary school at ISCED level 1.

The following terms may be used for educational establishments for this age group:

Preschool systems observe standards for structure administration, class size, student–teacher ratio, services, process (quality of classroom environments, teacher-child interactions, etc.) and alignment (standards, curriculum, assessments) components. Curriculum is designed for differing ages. For example, counting to 10 is generally after the age of four.

Some studies dispute the benefits of preschool education,finding that preschool can be detrimental to cognitive and social development. A study by UC Berkeley and Stanford University on 14,000 preschools revealed that while there is a temporary cognitive boost in pre-reading and math, preschool holds detrimental effects on social development and cooperation. Research has also shown that the home environment has a greater impact on future outcomes than preschool.
There is emerging evidence that high quality preschools are "play based," rather than attempting to provide early formal instruction in academic subjects. “Playing with other children, away from adults, is how children learn to make their own decisions, control their emotions and impulses, see from others’ perspectives, negotiate differences with others, and make friends,” according to Dr. Peter Gray, Boston College professor and an expert on the evolution of play and its vital role in child development. “In short, play is how children learn to take control of their lives.”