Adventures of a Teenage Dragonslayer (2010) on Netflix

Plot summary

Arthur is twelve, a target for the school bully, and his mother is fighting to keep custody of him from her devious ex-husband. A magical alchemist troll rescues Arthur, and Arthur finds a way to repay him. His mother treats the boy's talk of dragons as fantasy until she sees the danger is real, and then she joins the fight. With the troll, Arthur's friends Natalie and Tim, who make up the Knights of the Square Table, and Shane, a washed-up video-game master, they set out to deal with an unleashed dragon named Lord Darksmoke and the wicked vice-principal, Metz.