So that leaves two you can interact with, Marc and Kieran. Kieran niloach was a year ahead of Jason, and Marc justtobeme was two years ahead. They were both in Slytherin, and both on the dark side with Nathan. Though Marc is only pretending to be on the dark side. If Jason's involved with Nate's gang, he can use Al as a torture subject until Al is finally rescued.
As for my other kidlets, I don't see them interacting with Jason, unless they randomly bump into each other, which is always fun too!