From the age of 7, up to nearly 15 years old, I had selective mutism in school. Actually I had 6 occassionally whispered words, which were "Excuse me," "I;m sorry," and "Please stop." That was it.
I spoke at home despite the fact that the torture I endured there was worse than at school.
For my 13th or 14th birthday, I requested, and oddly enough received a cassette recorder. I recorded scripts from various plays, then made up my own plays, my own characters. Not long after that I bought a book that "changed my life"[seriously, the title and author are totally irrelevant and enormously embarrassing]
By practicing over the summer, by the time school resumed in the fall, I had found my voice.
Still was treated like crap most of the time though, but they gave different excuses. But anyway, that is how I finally broke 7 and a half years of mutism.