18. The teaching aid of claim 17, wherein displaceable tiles are provided in individually distinct colours to represent variations in vowel sounds of particular combinations of letters according to spelling combinations.
19. The teaching aid of claim 18, wherein an additional set of blank, neutral-coloured tiles are provided to represent any unpronounced silent letter in a word and each blank, neutral-coloured tile is used by placing it alongside spelling and pronounciation tiles of both the first and second sets of displaceable tiles.