Singing is a very subjective thing. Every adjudicator has different expectation and preference. Not every good singer is going to win.
I have some students that I really secretly wish them to win something. They have been working consistently hard and it's time for them to get recognised. There are some who have been winning all the time I wish them not to get anything. They need to learn that they can't take things for granted.
Failure is also an art. It can destroy the kid but it can also make them stronger.
Teaching the right philosophy and mindset to kids is a great art. I am happy with the result but I care more about what to do after that.
Not easy to be a good teacher.