All of my student characters are in the age range between 18 and 21, so it would not make much sense for them to interact with someone younger, except maybe Samael, as he is the type to help new students around, perhaps younger students with their studies, if he is asked by a teacher to do so.
As for Darius, he wouldn't really get interested in Rowan simply because he can control shadows-he knows of shadow magic, certainly, he just can't control it himself, so it would be unlikely for Rowan to end up in his class, which is how he meets students, mostly, except maybe by accident? Other was Darius can meet a student is if he was perhaps taking a walk and seen a student putting themselves in danger by experimenting with their powers without supervision. In this case, he would stop them, scold them, offer to help them if he can, or direct them towards someone who can if he can't, in that order :)
EDIT:
I have to appologize, but I had some shit go down on my university just today, and it's complicated and it's going to take time, about two weeks of it. It wasn't supposed to be like this which is I refreshed the plot page, but now it is, and I'm sorry, but I don't think I will be up for much for the enxt week or so.