Correct spelling


Correct spelling, explanation: the s in children’s is a possessive ‘s, so it does not act like the plural s suffix (like in dog -> dogs). Because of that, the word before the ‘s is not influenced by it. Also, it’s worth noticing that the s could not have been a plural s, because children is already plural. It’s very important to remember the apostrophe in words such as children’s otherwise they are incorrect.

Definition of children’s:
possessive word
1. belonging to children
I spend the whole afternoon cleaning children’s rooms and washing old toys.
I hate buying children’s clothes; children grow out of them almost immediately!

Incorrect spelling


Incorrect spelling, explanation: this form is incorrect because of several reasons. First, childrens looks like a double pluralism. What it means is that it looks like the plural s suffix is added to a word that already is in the plural (children). If the s at the end is supposed to be a possessive ‘s, however, it lacks the apostrophe, as it should be spelled children’s.