An Onset-Rime Approach to Decoding for Struggling Readers
I have had many similar discussions with teachers over the years, as well as having worked with many children who struggled with vowel sounds. There is a very good reason that some children have difficulty with vowel sounds. When compared to consonants, vowels are abstract, impermanent. They do not track naturally to speech patterns and are heavily influenced by the letters around them.
The go to instruction when kids struggle with vowels is to double down on instruction of vowel sounds in the hopes the child will improve. This approach is typical of what is generally called a traditional or synthetic phonics approach. Traditional phonics is based on the flat-structure model of language utterances which views the spoken syllable as consisting of phonemes in sequence with no intermediate structures of importance (Cunningham, et al., 1999).
The vast majority of linguists today, however, view the spoken syllable as having a hierarchical structure (Cunningham, et al., 1999). That is that a spoken syllable is not just a string of sounds, but also can be broken down to an onset (aRuss on Reading: An Onset-Rime Approach to Decoding for Struggling Readers: