Missouri Learning Standards
L.1. Communicate using conventions of English language.
L.1.B. Punctuation, Capitalization, Spelling
In written text:
2.L.1.B.g. Spell and use the plural of nouns by adding –es to nouns ending in -s, -ss, -sh, -ch, or -x
2.L.1.B.h. Use nouns that change their spelling in plural form