Have you heard this rhyme?
When two vowels go out walking, the first one does the talking.
True, there are a number of double vowel combinations in which the vowel sound it represents is the same as the ‘name’ of the first letter (e.g., ee-tree, ea-leaf, ei-receipt, eo-people, ai-rain, ie-pie, oa-boat, oe-toe, ue-cue). However, in actual fact this rule is only true around 45% of the time (or less than 36% if you just focus on the 2000 most frequently used words).
This means that at least around 55% of the time the rule is false:
au-saucepan, laugh, cauliflower
ei-eight, height, leisure
ie-chief, friend, sieve
ou-house, shoulder, country, soup, thought, dough, could
The rule becomes even less true when you follow the double vowel with an ‘r’:
ear-bear, earth, spear
Then you need to take into consideration all the vowel-consonant diagraphs – ar, er, ir, or, ur, aw, ay, ew, ew, ow, oy, uy – all of which have no relationship at all to the name of the first letter.
So, sure it’s a catchy rhyme and rhymes are a great way to help students remember concepts, but you have to question the value of teaching something that is not true most of the time and that ultimately students will have to ‘unlearn’.
Instead of teaching this ‘fake’ rhyme, look at other memory strategies for teaching students to remember the sound represented by different letter combinations such as using pictures and stories.
Clymer, T. (1963/1996). The utility of phonic generalizations in the primary grades. The Reading Teacher, 16/50, 252-258/182-185.