Question

fix the one plural or possessive error.
most childrens interest in stars wanes as they get older. but one childs fascination led him to study physics at harvard and astrophysics at columbia university. that child, neil degrasse tyson, became director of the world-renowned hayden planetarium in 1996.

Explanation:

The error is in the word "childs'". The singular possessive form of "child" (which is the correct singular noun, not "childs") is "child's", as we are referring to the fascination belonging to one single child.

Answer:

Most children's interest in stars wanes as they get older. But one child's fascination led him to study physics at Harvard and astrophysics at Columbia University. That child, Neil deGrasse Tyson, became director of the world-renowned Hayden Planetarium in 1996.