Phonics

Ehri and colleagues pooled 38 experiments and 66 comparisons and reported an effect size of 0.41 for systematic phonics, rising to 0.55 when instruction began in kindergarten or first grade and falling to 0.27 when it began later.

Phonics rests on the ability to hear and split sounds. Without that base there is nothing for letters to attach to, which is why phonological awareness comes first.

Method matters as well. Among children trained to sort words by sound, those who also handled plastic letters, linking sound to print physically, improved most (Bradley and Bryant, 1983).