This is a key Common Core Standard in Language for grades 1 - 3:
CCSS.ELA-Literacy.L.1: Demonstrate command of the conventions of standard English grammar and usage when writing or speaking.
Here are singular and plural nouns, holiday style! There are several noun pairs, some regular plurals, some irregular plurals, with several activities for the kiddos!
Come on over to Elementary Matters to see how to get this product at a reduced price in honor of my quest for Acts of Kindness during the holiday Season!