There are three ways to learn to read English - whole language, a phonics whole language mix and an Initial Teaching Alphabet. The vast majority of children are taught using a phonics whole language mix like Hooked on Phonics or Explode the Code. This approach yields consistent results "60% of our nation's children experience formidable challenges learning to read, and for at least 20-30%, learning to read is one of the most difficult tasks they will confront in school." (National Institute of Child Health & Human Development)
To find out why let's look at this MRI from Sally Shaywitz, MD of Yale, author of the Overcoming Dyslexia, taken while many children were reading.
The neurological definition of reading is connecting the word shape to its meaning. You see three dark areas that are very active. The front of the brain carries the meaning of the words the back carries the picture. For nerve cells that is a long way to go which is why whole language is so ineffective and why any mix of whole language in phonics is ineffective.
[If you are unsure if this applies to a program you are considering ask how they teach the student to read the word of. If they say we have the child memorize it you know the system they use is a mix of whole language (memorizing each word) and phonics (connecting a letter to a sound)]
However, the phonemic awareness area is in between the meaning of the word and the picture. It is already well connected to the speech area because it gives the phonemes to the speech area to be blended into words. Two-thirds of the connection is already made! All the non-reader needs to do is connect the phonemic awareness area to the word shape area in the back of the brain.
An Initial Teaching Alphabet (ITA) can bridge that gap because it links a sound to a letter-shape that is part of the word shape. Just as the speech area can blend the sounds, the shape area can connect the letters. The best way to make that connection is a phonics system where 1 symbol (letter) makes only 1 sound. This is done by using an Initial Teaching Alphabet.
An Initial Teaching Alphabet (ITA) is an alphabet that uses special letters for each sound. You have seen them in a dictionary's pronunciation key. Yet ITAs have one very consistent problem - transferring from the special alphabet to the traditional alphabet. And the problem comes late in the method so you do all this work only to find out you need to start all over again with a totally different approach. Even 100 Easy Lessons has a wall that some kids hit between lesson 60 and lesson 80!
This problem stems from the fact that up until Rocket Phonics every ITA used non-letters. Some children can transfer words with these non-letters to their traditional English counterpart and some children just can't. Programs like are so inconsistent they take 5 years to get to 5th grade level and fail 40% of the time. In learning consistency is king and most kids know it.