Here is a simple poster to help kiddos understand the different rules when changing nouns from singular form to plural form. There are obviously always exceptions to every rule, however these rules apply in most cases.
Why do we add S to some words but ES to others? And when a word ends with Y, how do we know whether to change the Y to I before adding the plural suffix? And why on earth does knife become knives? You can unravel these mysteries with six simple rules.