I did speak in class, but very, very quietly. I did not speak at all on the playground. I communicated exclusively with facial expressions for pretty much all of grade school. I was totally normal at home, at my friends' homes, etc., so long as there wasn't a stranger or more than a few people I knew there.

As master of none said, it is an anxiety disorder. That said, I do not think I would have appeared to be an anxious child. I smiled constantly and had many friends. I was not, in fact, anxious about anything else but speaking in certain situations. If you want to look it up and see if your child meets the criteria, you can look here: http://www.selectivemutism.org/faq/faqs/what-is-selective-mutism-sm and here: http://www.selectivemutism.org/faq/...child-with-sm-portray-in-social-settings