The point of teaching Sound Exceptions are so that children can identify Letter/Sound Patterns and use these patterns to figure out unfamiliar words.
For example, if a child sees the Y at the end of a word and the child knows that when the letter “Y” is at the end of a word the “Y” can produce a Long E sound or a Long I sound. The child will know that they can decode the word by using the consonant “Y” sound, the Long Vowel “I” sound, and the Long Vowel “E” sound for the letter “Y.”
When Y is at the end of a word it might not make the consonant sound and instead make the Long E or Long I sound. This is a simple Sound Exception rule to memorize and by knowing this children will be able to sound out words and read at a faster rate.
For more information about this example of a Sound Exception for Y, there are 3 videos about Y acting as a Long Vowel, there are stories for the children to read, and there are Flashcards for additional practice reading these Irregular Y words. (Y as a Vowel Video, Y as E Video, Y as I Video, Book 3 Stories, and Y as a E and Y as I Flashcards).