Severn Cullis-Suzuki now in her late 20s, started the Environmental Children's Organization (ECO) when she was only 9-years-old. ECO was a small group of children committed to learning and teaching other kids about environmental issues. In 1992 they raised their own money and attended the UN's Earth Summit in Rio de Janeiro. A then 12-year-old Severn closed a Plenary Session with this amazing speech that received a standing ovation. She received a lot of praise for her talk then—even Al Gore called it "the best speech at Rio."
The video below shows Severin giving a speech that is under 7 minutes to an international environmental conference back in 1992. Take a look and you will see that age is not a restriction on public speaking.