imagine two stars shining next to each other in a glorious clear sky, with just a full moon and those two stars. you will see them, appreciate them and fall in love with their beauty. but there will be a slight difference of which star you love more. both are sparkling and enchanting. but one seems to be dull in the presence of the other. because the other one, with its dazzling beauty, makes the second star less appealing.
now imagine the scenario on two kids in a school, two kids who are yet to be groomed. both are talented and bursting with potential. but one is more polished and confident than the other. the first kid is encouraged and given more opportunities than the other one, and the end the other kid ends up hating himself and being jealous of the first kid. that's the problem of the teachers (not all) who wouldn't uplift the ungroomed kid. whether its a stupid speech or anything, they will just give the opportunity to the prepared student because he can. and will not even pay attention to the kid who wants to and is willing to do it, because it will take time and effort to develop the kid into it.
now, some people will think that its not the first kid's fault that he is more confident and I am not saying he shouldn't win. it's not even the second kid's fault that he is unready for the chance. its the teacher's or the instructor's fault that he is not paying notice to the kid bursting with potential. don't they realize that a school/college is the place where people come to learn, they will not come ready for everything. if they are not confident, start to appreciate them for the small things. if they are not well suited for a thing, prepare them for it. that is your job.