What a great question! I intend to record a video response to this question this weekend, but for now...
The first thing I'd want to know is more about your 10-year-old. In what ways do you think he or she lacks confidence and needs to get more comfortable with public speaking? That's not meant as a criticism of your child -- he or she is ten, and skittishness with public speaking, to be kind, is rampant at all ages -- but a better understanding of your child's specific abilities and needs will help to inform a diagnosis.
That being said, I would encourage him or her to start by talking about familiar topics about which he or she is enthusiastic to people (close friends and family) he or she knows well. For instance, I am a HUGE Star Wars, Star Trek, science fiction and fantasy fan, and if we knew each other (or even if we didn't, hahaha), you wouldn't have trouble engaging me in conversation about these franchises and the stories I love to consume!
Once you have your child talking, introduce other friends and slightly less immediate family and acquaintances -- expand the circle, both to other people that are slightly more challenging to your child, as well as a more diverse group of topics. Gently, but consistently, widen the lens of the conversation so you are -- safely and gradually -- moving into the realm of the unfamiliar, considering new ideas and enjoying the process of exploring those ideas in a safe environment.
It's also important to introduce the idea, gently, of civil debate. Get your child used to the idea that people may not always agree with his point of view, and that's OK! Oh, the society we would live in and the things we could accomplish as a nation and a culture if we all could learn that lesson well!
I would also get to know the debate coach, explain your child's situation, and get his or her advice and feedback on the best way to introduce someone new to the team. As an experienced professional, I'm sure your debate coach has seen it all before and has some great ideas about how to expose your child to the team and get comfortable with the other kids and how they work.
My final, self-serving (of course) advice is (obviously), consider hiring a tutor! I've actually helped students around your child's age with this exact issue, so if I can be of further assistance or if you'd like to connect and discuss this further, please let me know!
Again, a great question! I look forward to reading other tutors' ideas and advice as well!
Brian K.
07/20/19