Yes, ‘Kindergarten’ can be considered a proper noun. In its original sense, it refers to a specific educational program or institution for young children, typically before they enter elementary school. When used in this context, it is capitalized because it denotes a particular type of educational setting.
However, ‘kindergarten’ can also be used as a common noun when it refers to the general concept of early childhood education without specifying a particular program or institution. In this case, it is not capitalized. For instance, you might say, ‘My daughter is in kindergarten,’ but if you’re referring to a specific kindergarten, such as ‘Little Stars Kindergarten,’ then it is capitalized.
In summary, whether ‘kindergarten’ is a proper noun depends on how it is being used in a sentence. If you are referring to a specific place or program by its name, it should be capitalized. Otherwise, it is generally treated as a common noun.