I've been doing a lot of thinking about the teaching of public speaking to children. It is more than just giving a speak. Just recently I asked my 16 year old to ask a question about a class he was going to take. After reminding him what exactly he needed to ask I also felt as if I needed to remind him about greeting the person, making eye contact, etc. His response was, "Can't you just do it?" That made me realize how important it is to work with all of my children on how to present themselves even to take care of simple tasks. Eventually he went and asked the questions and came back. I asked if it was as hard as he thought. (He would still prefer I do it for him.
Talking in our families is very different than going out to strangers or even standing up in front of friends. The way to help our children improve in this area is to watch how they do it and give them feedback. It is good to give positive and negative criticism. We are so worried today about offending someone or hurting our children's self-esteem that we often don't give correction. Practicing at home is good but it is not the same as standing up in front of someone else. Provide as many opportunities as possible for your children to learn how to present themselves. Simple things like shaking hands, making eye contact, not playing with your hair or clothes are all important.
For some people public speaking comes naturally but not for all. Start young and practice often!