Phonics instruction has a strong impact on the reading abilities of young children. Those receiving phonics instruction in the early grades (K-1) showed significant gains in their reading comprehension and spelling abilities and moderate growth in oral reading skills. Studies show that children in grades 2-6 also show growth in these areas, but theirs is not as considerable as that seen in primary grade students. At the upper grades, phonics instruction has a positive impact on the reading abilities of disabled, low achieving non-disabled students as well as those from low socio-economic backgrounds. These groups of children showed growth in their abilities to decode and spell new words. However, their reading comprehension skills were not affected by phonics instruction.
Diphthongs are linguistic elements that fuse two adjacent vowel sounds. English has four common diphthongs. The commonly recognized diphthongs are /aʊ/ as in cow and /ɔɪ/ as in boil. Three of the long vowels are also in fact combinations of two vowel sounds, in other words diphthongs: /aɪ/ as in "I" or mine, /oʊ/ as in no, and /eɪ/ as in bay, which partly accounts for the reason they are considered "long".