Use conventional spelling for words with common spelling patterns and for frequently occurring irregular words.

With an uncountable number of words in the English language, first graders need to know that they don't have to memorize the spelling of every single one of 'em. That's what grammar's for. Using all of the standards they've learned from kindergarten until now, first graders should be recognizing spelling patterns for regular words, but taking note of those irregular words that have their own quirky patterns, too.