As any infant pupil knows, c is for cat. Would it were so simple. C actually stands for a catalogue of spelling oddities, a cataclysmic reminder of how catastrophically complicated phonics can be.
When c is followed by e, i or y it changes to a "soft" sss sound - as in century, city and cygnet. This rule was brought over by the Norman invaders (all those smooth-talking d'Arcys and de Laceys), so that ever since we've had to write words like kettle, kilt and Kylie with a k.
C is also a main constituent in that chirpy cheeky chappy, the ch digraph - one of the three "extra" consonant sounds (along with sh and th) taught to reception children alongside the main sounds of the alphabet.
The trouble is that in words with Greek origins (such as school, chemist and Christmas), ch stands for a k sound. And in words more recently imported from France, it sounds like sh - witness chauffeur, champagne and Charlotte.
Not content with that, c and i sometimes get together to do the sh trick too - think of precious, magician, and special. It's all on account of the chaotic cornucopic nature of the English language. On the one hand, we have a rich, exciting lexicon drawn from languages all over the world; on the other, we have spelling oddities. Ciao.
* See Sue Palmer's guide to the sounds in English, in the new TES Primary magazine