Dragons
Of course it would probably be difficult to depict dragons well on the probable budget of this series. They would probably have to tell, not show, most dragon related incidents.
But it would be a good idea for the producers to buy the rights to "The Fifty-First Dragon" by Heywood Broun anyway.
http://www.bartleby.com/237/33.html
http://www.imdb.com/title/tt1164582/
If I was the creator of a series about young people in Knight School I would definitely want to buy the rights to "The Fifty-First Dragon" and introduce Gwaine le Coeur-Hardy as a minor recurring character. The protagonists might watch him practicing killing a dummy paper dragon and say he does it well but killing real dragons would be much harder.
Then the protagonists could go watch from a distance as he tries to kill a real dragon off screen and cheer as he succeeds. And then each episode could show the students congratulating Gwaine for his latest kill, or the news of it spreading around the school, or have a scene where someone looks at his scoreboard and see another kill for Gwaine.
And soon Gwaine's popularity would turn his head and he'd turn into a jerk jock who bullies the protagonists who would became jealous of his fame and popularity. So one by one in different episodes each of the knight school protagonists would put knock out drops in Gawine's coffee or lock him in his room and go off to slay a dragon and come back singed and weary but successful and tell Gawine he earned his fame the hard way and can have it and they're never going dragon hunting again.
And in one episode the person in charge would hear a report that dragons have been complaining to their government about the new and terrible dragon slayer and demanding action, and the dragon government has appointed a committee to form a plan to kill the new dragon slayer. The person in charge would keep it secret from the knight students and Gawaine so Gawaine wouldn't loose confidence.
I would plan for Gwaine to meet the fifty first dragon about the time the series ended, but I would also have a back up plan, to write a story outline for each of the main characters - in case the star wanted to leave the show or made too much trouble - in which that character becomes jealous of Gawine again and uses a spell to trap him in his room and goes off to slay a dragon just when the dragons have prepared a trap to kill the dragon slayer. Just in case it became necessary.