The same vowel sound is often represented by different vowel letters in writing. Vowels also change their sound based on where they're located in a word and what letters are around them.
◂English Language Arts Worksheets and Study Guides Kindergarten. Vowel Sounds
Students apply knowledge of language structure, language conventions (e.g., spelling and punctuation), media techniques, figurative language, and genre to create, critique, and discuss print and nonprint texts. (NCTE)