Question

What's wrong with the following? Stop. The glass is about to break above the kid's heads

Answer 1

"Heads" indicates that "kids" must be plural, but with the way the apostrophe is placed, it is singular. Instead of "kid's," it should be "kids'." Or the other way around – "head," instead of "heads."

Answer 2

The “kid’s heads” implies that there is more than one child there whereas an apostrophe for “kid’s head” shows possession of a kid’s head.