Common Core Standards
Grade 2
Reading RF.2.3.A
Distinguish long and short vowels when reading regularly spelled one-syllable words.
If your students are expected to tackle multisyllabic words in third grade, they've gotta nail down those vowel sounds in one-syllable words by the end of this year.
So, make sure your students understand that our five vowels can make about fourteen sounds, so that cute little pup should not be pronounced like poop.