Matryoshka said
Oh shoot, Heidi's the only first year, isn't she? Hey Vicier, as a first-year, will Heidi have less opportunities to interact with the other characters as they are upperclassmen and she is not only a first-year, but knows virtually nothing about being a daemon hunter whatsoever? And if so, should I bump her up a year?
Heidi will still have plenty of opportunities to interact with the upper-classmen. As mentioned in the information section, when the alarm sounds all classes are halted within the high school area meaning all the students have the opportunity to hunt together. The students choose if they want to hunt or not, if they don't want to it basically will become a free period for them and they can hang out with their friends.
Also each student from second year down will have net Erin because due to who her mother is she will have basically become the schools welcome community. So the two of then can be friends if you like.