Is childhood a proper noun

No, the Word 'childhood' is a common noun, a Word for the childhood of anyone anywhere.

A proper noun is the name of a specific person, place, thing, or a title; for example:

• Balfour Brickner Early Childhood Center, New York
• Childhood Lane, Shingle Springs, CA
• Museum of Childhood, Cambridge Heath Road, London, UK
• "Childhood", a novel by Robert Hartlay